I find it helpful to consider the physical analogy regarding work/productivity. Just like how Walking, Running, and Sprinting are very different levels of work,

I find it helpful to consider the physical analogy regarding work/productivity. Just like how Walking, Running, and Sprinting are very different levels of work, coding !== coding. Some codes are like a swamp; you have to sprint through it or else you won't make progress, while others are more like walking through a desert; running will simply burn you out. Andrew Huberman says that when it comes to focus time(high dopamine states, pupil dilatation, high brain activity), most people can only do two to three 1.5-hour sessions each day. (Note: this is high-focus work) Personally, I find styling basic CSS to be something that I can do with a podcast in the background. And for those tasks, I can do them for 3-4 hours straight without major problems. But when it comes to implementing something that I've never done before where I need that internal voice to be loud and clear, I might burn out after an hour or so. Also, since you mentioned 1-2 PM, I'm wondering if your lunch can potentially contribute to your crash. Are you drinking coffee right when you wake up? Are you eating lunch and laying down? Are you getting proper sleep?