Remember that your brain is setting baselines for how many endocannibinoids (our body's internal cannabinoids) it needs to produce to keep everything functioning normally.

When you smoke, vaporize, or ingest cannabis your body gets a sudden boost in cannabinoids giving you the feeling of being high, but your body reacts by producing less of its own cannabinoids. The result is the faded, fuzzy feeling that constitutes a cannabis 'hangover' after the high.

Allowing your body's endocannabinoid system regain balance by not smoking or ingesting for a time you can achieve the same 'high' as your first time.

Flooding your body over and over again will eventually build up cannabinoids in your system to the point where more wont do as much, but you will feel the need to smoke or ingest to maintain a baseline for your brain to feel like it is functioning normally. Your body will have considerably slowed its own production of endocannabinoids.

Not really an answer for how to get your tolerance lower, but why your tolerance gets high (no pun intended) in the first place.