If you smoke during the early morning or late night before bed, your brain is in the beta/theta wavestate...its a state that is not completely asleep and not awake either...its the time your brain is most active and you get very high and your tolerace is much lower at these times. Most people smoke during the day with people which i think is why they dont get as high.
I smoke 2-3 bowls on my own (almost always at night or in the morning
) and however much is around with other people (usually a joint or 2 and a few bowls)