I made an account to post on this because of all the misinformation on this esteemed site by almost all members except S.A.M. Basically, all actions you do, such as riding a bicycle or shooting a free throw, builds pathways in your brain. The more you do a certain action, the stronger the pathways get and the easier said action becomes. This is why, as the saying goes, "practice makes perfect." The stronger these connections become, the more used to the action your body becomes, allowing it to perform the action easier and with less focus. Also, the little tiny parts of your brain that allow you to get high, your cannibinoid receptors, get more used to the effects of the high, the more marijuana you smoke. SWIM smoked everyday for the past two years and can't get nearly as high as they used to. No one can. This is an effect of long term frequent use of most drugs; however, harder drugs, such as heroin, have a much unhealthier reason why. Whereas cannibinoid receptors just get used to the effects of THC and the high, therefore making them less noticeable and much more containable, Heroin actually wears away at it's receptors, numbing and killing them over time, and hurting the brain. This is why no matter how long of a tolerance break you take from these harder drugs, you still won't get the high back. With marijuana, if you take a break from smoking for a moderatly short period of time, the effects of the high you want, such as the stronger motor impairment and the giggling, will come back. They won't ever be as strong as the very beginning, because now you know what to expect with the high. The effects will however increase drastically.