I read this from Seth Godin in one of my favorite books, Manage Your Day-to-Day: Build Your Routine, Find Your Focus & Sharpen Your Creative Mind: 

Lots and lots of people are creative when they feel like it, but you are only going to become a professional if you do it when you don’t feel like it. And that emotional waiver is why this is your work and not your hobby.

• Substitute the word spiritual for the word creative, 
• substitute the phrase truly transform for become a professional, and
• substitute the word life for work… 

… and you have the secret to spiritual transformation:

Lots and lots of people are spiritual when they feel like it, but you are only going to truly transform if you do it when you don’t feel like it. And that emotional waiver is why this is your life and not your hobby. 

That’s why I believe that the best thing we can do as spiritual people is choose to become “professional Christians“, and do the work, day in and day out.