[keyP]

Depending on your situation, the other answers in this thread may help. Assuming they're not viable for you, you could try reframing the situation. You now have something to look forward to on your off time that can be used to help during difficult times at work. Also, working on a project that you like all the time could maybe make it less appealing over time, similar to over-listening to a song. Maybe you haven't realised it but the immersion you have could be because you have breaks in between sessions for work.