My personal theory is that yes, the strain affects the high, but so does your physical status going into a session.

So, let's say you're hungry or tired or whatever ahead of time, then you smoke. Smoking makes your sense of time and your perceptions of your needs more intensified, so you might end up meeting needs you would normally ignore, such as hunger, fatigue, etc. I find that it "reveals" my personal needs to me and makes me prioritize them over other things.

So sometimes I end up cleaning my house, painting a picture, reading a book, etc but if I'm tired I just want to sleep.