- Choice of wrong career.
- Choice of incompatible partner.
- Not speaking your heart out to someone you really love (out of fear,society or embarrassment,nothing hurts bad enough).
- Not doing what you love.
- Not traveling enough.
- Living under pretense of your ego and dying under it with nothing real accomplished.
- Living an unfruitful life just to meet standards of society by pursuing money and money only and leaving all bliss behind.
- Playing mind games in matters of heart.
- Living according to other people perspective and will.
- Not falling and failing in love,the true love.
Source: What is the greatest mistake you can ever make in life?
Life Lessons, Love Hacks 