Then after spending a few years in employment, the environment getting more and more toxic (and less and less about technical excellency and more and more about dirty politics), you can lose sight of how that stress gradually eats away at you. Ultimately, I just couldn't work anymore, I couldn't focus. I started having panic attacks. I was completely lifeless, fatigued all the time. I would later find out that my endocrine system had become completely out of whack. Long story short, it took me well over an year to get to be barely functioning again. I had a lot of anxiety symptoms, and clearly fit 100% most technical descriptions of burnout (but don't put too much weight to it, after all burnout is just a label attached to a set of symptoms). But worst of all, you become very cynical. Your brain gradually gets rewired to model the world as a cold, harsh, evil environment, where most everyone is against you. You end up in a state of learned helplessness, you fall victim to avoidant behavior to sooth this permanent state of doom that you're feeling.
The way out is learning to relax. Learning to rewire your brain, to have fun again. Learning to solve your anxiety problem. Following the steps from a book like "Anxiety & Phobia Workbook" by Edmund-Bourne is almost mandatory. Exercising regularly is mandatory. Depending on how deep you are in the hole, how much social support you have, this may be one of the hardest thing you achieve in your life (keep in mind that most drug addicts never make it out alive - see "In the Realm of Hungry Ghosts" by Gabor Mate).
In short, it may be that you stress yourself too much. Life can and should be a joy. What I've described above is my experience, which is closer to one end of the spectrum, but even if your issues are much more minor, the same rules apply. But again, the chances are small that anxiety is the source of your issues, given the limited information in your post.