Risk It or Not?!?

A while ago I hear this, "learn from others mistakes because you don't live long enough to make them all yourself" or something like that.

But here's my dilemma, how do you know what decisions you should take a risk on and see how it goes or play it safe because you know what is probably going to happen next (based on others experiences)?

I don't know if I made any sense but I'm a little bothered by it...