Do you often doubt yourself? 
 or Do you have low self-esteem? Overthinking affect your brains. It also affect our emotions.  If we did'nt handle our emotions, it might also affect us socially and physically.  Don't think of what can go wrong, but what can go right. Distract yourself into happiness, Stop waiting for perfection, Change your view of fear, exercise and concentrate properly.  Lets do it.  Aja!