One of my success mentors, John Assaraf, has a saying that I love: "When you're interested in having something, you'll only do what's convenient; when you're committed, you'll do whatever it takes."
I have kept this mantra top of mind when I am setting goals or find myself not achieving one. I ask myself, "Am I willing to do what it takes to achieve this goal? Am I doing what is convenient, or am I doing what's necessary (and out of my comfort zone)?"
There's a reason why not everyone is successful. It's because not everyone is willing to do what it takes.