There are many traits about people that you want to watch out for. People with negative traits can be catastrophic to your life if they have influence over you. 

Why is that? 

Because 99% of the time it will lead to failure.

They may succeed for a short while, but it won't last long!

Also learn from exemple: How Travis Milton went from saying he was beating Elon Musk, to losing everything in a matter of 1 year? - That's the true example of a delusional person and you must watch out as the world is filled with these same people.