Think about someone very special in your life, someone you Love so, so much. But because of your personal needs you are on a trip and cannot see this person for now and you want to see him or her again. You want to spend time with him, to share your love with him.
Yearning can be a very trying emotion, or it can be a very helpful, even warm and enjoyable experience.
When you focus only on what you are missing you will most likely become sad, hurt that you do not have your love with you. But you can also look to see how fortunate you are to even know such love, most people don't. Then you will be focusing on what you do have, albeit not in your "hand" right now.
There is a prayer we say at mincha on Rosh Hashana that includes such tender, yet pressing requests: "Beloved of my soul, merciful Father…. Glorious resplendent One, Light of the world, my soul is lovesick for You, I beseech You, O'G-d, pray heal it by showing it the sweetness of Your splendor…. I have been yearning to behold the glory of Your majesty. These my heart desire…. Reveal Yourself my Beloved…the time has come and be gracious unto us ….
On one side we long so much for Him we could even, G-d forbid, become sad… sad that we do not have the immediate experience of His Shechina (Revealed Presence). But also, we thank G-d that we know such an experience is possible. We are so blessed to know that we could see that He is truly present, that we have in our soul the knowledge that this most glorious vision can happen.
Even as we yearn so much, we thank Him for allowing us to know that He is here to be yearned for.