Mental exhaustion

I am tired mentally for searching what I want. I feel useless after years spent in countless hours at night time when my kids fall asleep to read pages of course notes. After I completed the study. Nothing memorized in my head. Everything just accomplished for a piece of certificate that is even not giving me any chance to contribute what I have learn. Sometimes I feel it is unfair. I feel I have been cursed for all those happened in in between 2001 - 2004.