Normally we do mistakes and also learn from our mistakes. But sometimes it take a lot of time to realize our mistake due to our own ignorance or ego. At times we thinks that we know everything and because of this we didn't listen to correct advise sometimes.
Sometime we do mistakes due to laziness (i.e. purchase useless insurance plan or ULIP without understanding them), sometime we do mistake because we trust some person and got wrong advise (mostly happens in sales).
Making mistakes is not a crime but not learning from the your own and others mistakes is definitely. I also did lot of mistakes in my financial life but here I am writing about the major ones.