Destiny/Choices in life?

Is there really anything called "Destiny".

I know that a lot of people say something like "whatever happens, happens for a reason".
I don't know if it is just to make someone feel better and not think much about what has happened / if there is really something called "destiny".

A lot of times, I used to believe that your life is dependent on the choices we make.
And thats how my life seemed to me so far.
I believed that God would show you a direction , but it is upto you about what kind of efforts you make to get it/reach it/achieve it.

Inspite of many efforts,I really do not understand why certain things do seem so tough.
Is it just the time which would answer everything or Should I really believe in "destiny"?