I was taught something that relates to this once...

A definition for the word "character"

Character:
Following through on a decision long after the excitement of the moment has past.

The beginning of most things is exciting. If we are passionate about it and hold character we will continue even once that excitement fades for a moment. If we are very passionate we will continue to be excited.

Sometimes it is as simple as picking only one thing to be passionate about. (harder than it sounds)