Discipline is the key not motivation. There is a lot on the topic of "Motivation vs Discipline" just do some research, but here is a link to one I find to be really insightful http://impossiblehq.com/get-disciplined-not-motivated Hope this helps as it really helped me when I was going through a similar situation.
The thing with motivation is to not rely on motivation! Instead, you must force yourself to keep going. Keep making, regardless of having a desire to make. We have more on work habits here: Motivation is Bull Chuck Close also has some great advice on this,…