Simply put, motivation doesn't work for long, and isn't always going to be there. It is more of a wave that comes and goes. However, being consistent despite of these waves WILL get you to where you want to go. Show up on days where it's easy and go hard, show up on days where it feels impossible and take it easier. The continuous conscious effort of forcing yourself to go is something that will become a part of who you are and how you operate. If its 15 minutes of moderate effort or 60 minutes of intense effort, creating and maintaining the habit is going to become the motivation.