I've got an overactive brain. I enjoy work, I enjoy life, and I'm not good at relaxing. I've also never slept very much due to this overactive imagination and my brain constantly thinking.

This person has an “overactive brain” meaning that their mind is occupied with activity most of the time. Because of this, they don’t often relax and find it difficult to sleep. They find joy in both work and life, but their overactive brain does not allow them to slow down.