Here's 3 reasons I believe why we make bad decisions.

By bad decisions, I mean those which contradict the ones you've made in the past that you are proud of. (aka the good decisions)

Like standing up for the right thing. Helping the needy. Saying no to temptations. Staying physically fit and mentally well-balanced.  

I bet everyone has a phase when they act against their own good habits. A good habit or a bad habit is always a choice. We make choices very quickly in the span of less than 10 seconds. So in that brief time window, you have a choice. And generally we make the right choice.

But here's when we tend to make bad choices according to my own experience:

1) When you are tired

2) When you are scared and desperate about something

3) When you are disillusioned about life and that you conclude it has no real meaning

What else? What are some other thoughts you have on why people make bad decisions?