I used to feel like this person, and I'd find myself alternating between burnout and enthusiasm every few months as project work ebbed and flowed. Going between

I used to feel like this person, and I'd find myself alternating between burnout and enthusiasm every few months as project work ebbed and flowed. Going between the two peaks was exhausting and every crash back down to burnout felt horrible. My solution was to go and do something fulfilling in my spare time, force myself to stick at it, and not work a second longer than I was obligated to. Keeping my mind busy and satisfied over a longer period of time forced the "work thoughts" out of my head eventually, and made it much easier to detach at the end of each day. Working from home meant I could turn my 1 hour commute each morning and evening into 2x1 hour to work on something fun for myself. A few months of doing that and I started to feel substantially better, I'd even look forward to the slow periods that would previously have bummed me out - at the end of the day the bastards still have to pay me, and I have less work to do so it's a win-win for me.