In general I moved from a model where the limiting factor was absolute number of hours worked to quality of peak hours in the day, where (I believe) the latter is much higher variance and also significantly affected by not having sufficient sleep. I moved from taking modafinil (which never helped me) to taking melatonin (which helps a lot), and always letting myself sleep in as much as I need. I think this has helped a lot.
In general I moved from a model where the limiting factor was absolute number of hours worked to quality of peak hours in the day, where (I believe) the latter is much higher variance and also significantly affected by not having sufficient sleep. I moved from taking modafinil (which never helped me) to taking melatonin (which helps a lot), and always letting myself sleep in as much as I need. I think this has helped a lot.