Everyone has diff. highs and tolerances towards cannabis, you can't assume that every weed you ever smoke makes you motivated, because they make weed that can be a cerebral uplifting high (may be what you smoke) and then you got the weed that gives you the "couch lock" where you don't want to do shit....When I smoke "mids" most of the time it makes me "couch lock" or gives me a headache, but when I smoke some killer weed (some dro) depending on when it was harvested, it gives me more of an uplifting high and i've had the same strain of killer and it gave me "couch lock" So presumably a lot of times it's all about the strain, genetics, harvest time (trichome cloudy:amber ratio), % of THC....There are many factors kinda hard to single out 1 reason.....Just take everything into consideration....I'm no expert but these are just some things I have learned from this wonderful forum site!