I know this feeling you are talking. On Scrum there is a phrase that can help. Consistency reduces complexity. How i apply this is to automate my behavior in these circumstances. If I dedicate 1-2hours a day on my project. I just do it as always, same place, same time, focus on the project, and timeboxed. That makes me work and not let being down by these feelings. Just keep doing it. On the other hand, one thing that works for me, is to just walk outside and have fresh air, little hikings ;). Hope it helps!