I have figured out that the cannabanoid receptors in your body absorb Anandamide. So this means the THC is plugged into your receptors. Once you get to the high 'plateau' your receptors are full with THC all in them like a parking lot full of cars. They must BREAK DOWN the thc already there, so when you're smoking and you are actually as stoned as possible and start to break down those THC particles you can't absorb any more. So when you just get sober halfway through your session is because you just finished breaking down the old THC. Basically all the smoking before was pointless, because the THC stopped affecting you. Sorry I am really high.