The concept of burnout has always been an interesting one to me. How do you know when it hits vs just having a bad day/week? Personally I think its about retrospective. Looking back and reflecting on the months and years you can identify the trends. You can view the timeline of your career and life and what got you to this point now. By reflecting on past choices and mistakes it can offer a small step forward. I find some semblance of understanding by turning thoughts into words on this blog.
For me, burnout is more than just physical and emotional exhaustion. It is more the depression around spending half your life writing code, first for fun then for living, only to realize is this really what I want to be? The idea of wasting my 20's and early 30's at simple engineering jobs and starting failed company after failed company is what is the most draining(are they really wasted? thats a reflection point for the future). Day in and day out not learning anything. Not spending your daily allowance of creativity and problem solving brain power. The acceptance of mediocrity cuts deep. I also think the fear of change is what keeps me locked in place at times, and its not lost on me.
I realized my own struggle with burnout a few years ago. Its still a struggle to find any passion in being an engineer. Maybe its the simplicity of the problems being solved, or lack of career evolution; I am still finding that out. But I have found something that helps. I now say yes to almost everything, because I never know what I will like or what just clicks. From writing this blog, to building games, writing tutorials, streaming on twitch, writing fiction, public speaking or building stuff. I found being open to everything forces you out of your comfort zone. Comfort kills creativity.