I treat the game as following:

When I have spend a lot of stamina to get a hero and I don't get it, It maybe is not in my account to get it.
So I try other things that maybe are in my account to get, since all is balanced in the end; ergo I must be lucky somewhere else!

This point of view does not say that my account is pre destined, but it does give me an option to move passed some things.
Maybe you could try this approach?