Do you take time to rest every so often? I used to work 7 days a week on my SaaS but now I make sure to take some time once a week to have a day off, to relax, to mediate, have drinks, see friends, etc. No code for a whole day.
What is the cause of the burnout? What exactly are you struggling with?
I just spent the last couple of days working extremely hard on getting a major version of my project released and now I don't really feel motivated to work on code. It happens every so often.
It just sounds like you're tired. You're human, not a machine. Give yourself a well-deserved brain break.