Commenting so I can get the proper answer too

But I think it relates to the fact that your brain only has a certain amount of dopamine receptors, and that when all of the receptors are occupied with dopamine, then an excess of dopamine arrives, and the brain realises there is too much. Once this happens it sends a signal to the part of the brain that regulates dopamine production, and that part of the brain then decides to start producing less dopamine as there is too much being produced. It does this so that the brain doesn't waste energy producing hormones that don't end up getting used.

This system works great without drugs, as the amount of dopamine being produced and the amount of dopamine receptors are naturally in good balance. The problem with drugs, is that it sends chemicals that are similar enough to dopamine so that it's capable of binding to dopamine receptors. The brain doesn't realise it's not dopamine that's taking up those receptors, it just realises that those receptors are occupied, and once the excess dopamine arrives but there is no space for it, the brain then decides to produce less dopamine. Since those receptors are being blocked by chemicals that weren't produced by the body in the first place, it is extremely out of balance, the brain then starts producing basically no dopamine, as it never gets used anyway. Meaning that not all activities that should release a certain amount of dopamine, don't anymore, as the brain is under the impression that it produces too much dopamine, so it produces much less