My psychologist explained that it is hard to feel happy, satisfied, or fullfilled if you’re exhausted. Happiness required energy.
Students who have just finished a long exam are a great example. They’ve just spent hours focusing as hard as they can, and they’re all exhausted. Not many would describe themselves as happy immediately after.
Hyper focusing can use a lot of energy even though you’re not aware of it. When you finally stop, you become aware of just how little energy you have left.
My psychologist recommended mindfulness. Recognise when you’re exhausted, be aware of the causes (lack of rest, food, water…), and accept that it will take time for you to start feeling better again.
Understanding what’s happening can make the symptoms more bearable.