The above question has been really itching me for some months now. Sometimes I play a one hour session and I'm very tired, then I play 3-hours-sessions and I'm not tired at all, so it's quite different. Because I'm not a pro I'm sometimes very tired in the evenings and then rather let it go than forcing me to play a certain pensum. So I don't really have a plan, maybe that's the problem ...
So what about you? Do have a strict plan (even if you are an amateur) you are sticking with or do you play just for fun when you have time and let it go when your girlfriend rings?