It depends on how long you've been observing this. It may be just a coincidence. I believe we are responsible for our feelings of motivation or any other kind of feelings, not the planetary positions. Our feelings do not depend on where the planets are in given times. They mostly just influence the energies that can make certain types of events more or less likely, like "opening the doors" (or "closing") for these events to happen. They don't control or are attached to our feelings.
So I'd say, just seek to make an effort to become more motivated in times where the Moon is more favorable. Perhaps seek alternative sources of motivation, or try to figure out things that could be interfering in your motivation. In order for us to accomplish something, we just need to get started, and this often seems to be the "hard" part. But once we give ourselves a push and get started, it becomes easier.
It could also be that, assuming that you're observing the current Moon sign everyday, you feel more detached when you know that the Moon is not in a favorable sign because there is no "pressure" of starting your project anytime soon. Whereas when it's in a favorable sign, you feel like: "This is the only time for me to start this. I can't fail". And this becomes overwhelming for you. That's just a possibility.
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