Start by identifying the root cause of the burnout. I feel like programming itself shouldn't burn you out. It's usually other parts of coding for work that lead to burnout. I've interviewed thousands of developers over the years for books, research, jobs, and if I had to choose a single culprit I'd say the most common cause of programmer burnout is a really terrible codebase that viscerally painful to maintain.

I did my best to illustrate that here: https://twitter.com/AndrewStellman/status/896405621494382593

Tangled, nasty, poorly maintained code is not an easy problem to fix. The first step is getting everyone on the team -- and especially the boss -- to recognize the real problem, and accept that fixing it will save more time than it costs.