To succed in something you have to dedicate all of yourself. Passion or enthusiasm isn't enough - you have to dive into the subject and keep on swimming until you reach your goal, because if you stop - you drown.
No one has ever reached his goals without getting through struggles. Others try to avoid them but i like getting into problems, they build my personality and knowledge.

The only thing you should be afraid of is being hesitant.
As Endy Bernard said: "I wish there was a way to know you were in the good old days before you actually left them."