Why? I have never had a high that lasted more than a few hours?
Remember the joke on the Taxi TV series where Ignatowski was a model student in college and turned into a brain dead zombie after he started smoking pot?
There is a lot of truth to this. I personally have seen it. Very sharp people end up being brain dead bums for many years and it all started with pot.
You're doing it wrong!
I kid, but for real: If you eat mangoes an hour before ingesting pot, it will temporarily weaken the brain-blood barrier and get more of the active ingredients to the receptors in your brain.
This is caused by the terpene Myrcene.
Of course, Myrcene is already present in cannabis, but at different levels, and a strain with a ton of THC and no Myrcene will not get you as high as a strain with less THC but more myrcene.
Please note that there is a complicated interplay between many of the terpenes in cannabis. Some are antagonistic to one another, and some are the opposite.
Personally, I can't wait for stoners to invent a strain of pot with ZERO THC. I am more a fan of the various terpenes than anything else.