The first place we need to look when we feel a lack of motivation, is our thought process. If we have conscious reasons impeding our progress, those must be dealt with first. This includes, in perhaps the most interesting example I've experienced, an association between recording and stress. It used to be that whenever I set up my recording interface, my palms would automatically begin to sweat, because I hadn't yet learned how to lighten up the perfectionism of the recording process.
If we can't find any conscious reasons obstructing our progress, this is where we need to look a little deeper. The reasons could be subconscious, resulting from pressure generated by others, or by our own feelings of inadequacy. More often than that, however, the reasons are physiological.
It is not at all difficult to break down the "inspiration" experience into a potent cocktail of neurotransmitters, with dopamine being perhaps the chief among them. In order to take command of the motivation process, we have to look at lifestyle changes we can make in order to encourage the production of those neurotransmitters. This includes everything from WHAT we practice, HOW we practice it, WHEN we practice, all the way to dietary habits and how much sleep you get.
For a detailed list of examples, take a look at the following video I put together. If you follow all the habits listed here, you'll see a marked increase in motivation. Guaranteed.