1- Lack of Faith.
2- Lack of Wisdom.
3- Lack of Confidence.
4- Lack of Patience.
5- Lack of Trust.
6- Lack of Money.
7- Lack of Luck.
8- Lack of Alcohol and Drugs for addicted people.
9- Lack of a lot of things that I won't tell.

What can also be considered here would be:
1- Broken heart.
2- Failed Love Story.
3- Losing Job.
4- Divorce.
5- So Bored.
6- Have nothing To Do.
7- Got a lot of money, but not happy.
8- Decide to go to hell.
9- Looking for a change.

and don't ask me why I stop at no.9 in each list, don't give me a good reason to commit suicide now !!!