Love is a mystery at the beginning it is rosy, passionate, intense, looks great and beautiful. The new couple seems to fond of each other so intensely, after they get used to each other seeing each other strength and weaknesses, like and dislike, after some weeks, months and years it leads to intense anger, hatred, pain, agony, insanity even death.

1)Relational Abuse
Relational abuse can be defined as the repeated mistreatment of an individual or person. The common examples of relational abuse include: Verbal, emotional, physical, and/or sexual abuse. Pathological manipulation. Pathological Narcissism. Pathological passive-aggressiveness. Excessive control and dominance and much more. All these abuses if tolerated for a long time without immediate proper solution it reduces affection, mutual interest, care, emotional love in romantic relationship.

2)Life Habit Abuse
Life habit abuses are traits which, although may or may not directly involve the partner (such as a secret gambling addiction), may ultimately affect the relationship in a destructive way. Examples of life habit abuse include: Drug addiction. Alcohol addiction. Gambling addiction. Sexual addiction.

3)They get carried away
This is also another reason why relationship starts great but turns sour later on; when a relationship is new, both partners are there for each other but it doesn’t continue this way; after a while they let things come in between them and their partners, and most times this happens subconsciously; it could be kids, career, school or just anything; when you love it more than you love your relationship, your relationship would definitely suffer.

4)Differences in Priorities
Your partner has different priorities and expectations regarding the relationship.
For some, the significant-other relationship (and family) is the primary center of gravity of life. Nothing else comes close in its importance.
For others, a romantic relationship, even a committed one, is but one facet of life. There are many other aspects of life which, in their perspective, can justifiably take higher priority.

5)Moving Through Life at Different Rate( speed)
When one partner is learning and growing at a rapid pace, while the other is stagnating, this may be a source of relational divergence. One example of this would be a partner advancing quickly in her career and society, while her significant other is stagnating at home.

The professional and social circles of the couple begin to diverge, and soon the couple themselves differentiate. They have physically, intellectually, and socially grown apart.

6)They didn’t grow with the relationship
“In relationships most times, at the start it is well fed but after a while, couples stop feeding it with vital relationship needs and this would dampen the growth of that relationship hence making a sweet relationship to turn sour.

7)They stopped understanding each other This is also another reason why a relationship that starts well doesn’t always remain so, when a relationship starts, both partners try to understand each other but after a while they lose sight of this and this would lead to the fight, quarrels, arguments and the whole drama that surrounds relationships.

8)Grown Apart, Boredom, Staleness, Rut
If any of the four terms written above resonates with your relationship experience, there are a couple of elements to consider:
If you have been in a relationship for two years or less, and you and your partner have “grown apart”, it could be due to a lack of commitment, different expectations, lack of compatibility, or the natural process of trial and error in mate-finding.

If you are in a long-term relationship, it is possible that life obligations (such as school, work, and especially child-rearing) got in the way of couple connectedness and mutual evolvement. A classic example is the “empty nest” syndrome, where after all the children have grown and left home, the parents suddenly feel like strangers to one-another, having not focused on each another for so many years.

9) Compatibility In Relationship
Relationship compatibility is a big issue while some couples or new found lover couldn't take their relationship to the next level. The success of any relationship is its compatibility.

The relationship compatibility link to different factors and several perspectives, including compatibility in intimacy, compatibility in personality types, and compatibility in attachment styles, lifestyle compatibility etc. Any relationship that lack the glue of compatibility it might cease to exist sooner or later or have several problems popping up often time.

10) Communication Issues
This is a big problem in every relationship. Numerous studies have identified communication (or a lack thereof) as one of the top reasons for couples therapy, as well as one of the top reasons for break-up and divorce.

Dr. John Gottman of the University of Washington, a foremost expert on couples studies, concluded that after over twenty years of research that the single, best predictor of divorce is when one or both partners show contempt in the relationship.

Contempt, the opposite of respect, is often expressed via negative judgment, criticism, or sarcasm regarding the worth of an individual. In communication studies, this is known as being “tough on the person, soft on the issue”.

Contemptuous communication works like poison - it destroys the health and well-being of a romantic relationship it squeezes life out of the relationship which resulted to sudden death - the end result is heart break, separation and outright divorce.

11)You no longer put your partner first
If you observe, when a relationship is new couples do things just to please their partner in order to make them happy; the man goes out of his way to show that he loves his lady and the lady does same; the problem is when the zeal to do this drops, the relationship would die gradually; when one starts waiting for the other to show more love then the relationship might slowly but steadily burn out like a candle.

12)Selfishness
Selfishness is also another relationship killer; selfishness is what would make one cheat on his partner; selfishness is what leads to misunderstanding and quarrels in relationships; thinking of yourself and yourself alone is selfishness, selfishness occurs in different ways in relationships, and it sinks the ship of relationship gradually and for a relationship to forever remain sweet, selfishness should be far from it, and by selfishness I mean selfishness of the mind.

13)Money Issues
The longer a couple has been together in a committed relationship, the greater the possibility of financial incompatibility. According to research, differences over money is one of the top reasons for marital dissolution . A couple also doesn’t need to be married to have money challenges.
Money issues and disputes tap into some of our deepest psychological needs and fears, including and not limited to trust, safety, security, power, control, and survival.

14) They think that honesty is not important.
Telling a white lie won’t end a relationship, but dishonesty about important issues shows a lack of respect for your partner’s feelings. Continued dishonestly leads to mistrust, upset and anger, so it is important to be open during difficult times. In a strong relationship, you should be able to say yes to both of these questions: do I trust my partner to be honest? Can my partner expect the same of me?

15)They are emotionally immature.
Relationship maturity doesn’t come with age; it is a willingness to work at a relationship, accept blame, and compromise. Beware of starting a relationship with someone who gets angry over nothing. At the beginning of a relationship, most people try their hardest to avoid fights, so be aware of how they behave in certain situations, or how they treat other people. Sometimes emotionally immature people are willing to learn how to mature and grow, but be careful, pushing or forcing someone to change is also immature.