Why does weed make you sleepy?

Everytime I seem to light up, I feel sleepy after

That's the usual experience when smoking Cannabis Indica or an Indica-heavy hybrid. It has something to do with CBN and CBD, two of the cannabinoids present in the weed. Cannabis Sativa and Sativa-heavy hybrids have much lower levels of these substances.

When I smoke Sativas, I feel like getting up and dancing or taking a hike in the woods. When I smoke Indicas, I feel like sitting on the couch and nodding off.

Seems to effect a lot of people that way regardless of whether the strain they are using is Sativa or Indica.
To what degree that effect is, depends on a lot of things including one's general physiology, state of physical wellbeing and so on.
Over time you can expect variations on the theme.
Certainly though, one can help facilitate, to a degree, the desired effect by choosing one strain over the other...

Well, some folks anyway. Not this 'ol sailor dog.
Smoking pot always wires me.
Hmmm, maybe it's a side effect of my last cloning...

smoking has the exact opposite effect on me. i can't smoke before bed.. i won't fall asleep.

OMG , now I have to choose between you and Vicki,

http://www.marijuana.com/vaporizers/94435-bag-vs-whip-both-equally-healthy.html#post881307 - Posts#'s 3 & 4,

hmmm, or do I?
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So would schwag have more of the Sativas, and nug would have more on the Indicas? because schwag/reg (i dont know what you all call it on here) makes me want to go crazy, and nug/crippy makes me want to chill.

sharing is caring!

No. The difference between schwag and nugs is in how the plant is grown and processed. Schwag is allowed to pollinate and produce seeds. It rarely has top-quality genetics. It's rarely cured. It includes leaves along with the buds. It's just not as potent.