We don't actually like comparisons. They’re always off but sometimes you just can’t do without. In order to understand the principle we have to exemplary break down complex systems and uncover simple correlations.
Let’s compare our brain to a traditional agricultural irrigation system. They’re canals that keep on branching off, flood retarding dams that open and close according to an elaborate system and farmers who, from generation to generation, carry on thousands of years of knowledge on how much has to flow when and where and where it shouldn’t.
Now to the brain: It also has line systems. You could conceive them as bio-circuit-boards. There is slight electricity in connection with chemical processes. A stop and go principle, that supplies matter, which is going to be symbolized by farmland and chemical messenger substances symbolized by water.
Dopamine and noradrenalin play a big role. We will not go into the details of these substances, we will concentrate on the fact that they trigger the expectation and fulfillment of happiness reactions in the brain. Principally that’s not bad, as long as it’s modest. To keep it that way the canal system only let’s a compliant dose pass through. Afterwards you need phases of neutral sensitivity. Otherwise you would even become emotionally blunted to happiness. If you are so to say “underlucked” you have to do something to change that or you’d have to be lucky and something pleasant would have to happen to change your mood. So far everything is normal.
But when drugs come into the equation you can have to think of it this way: With tremendous pressure way too many trigger substances are pressed through the canals.
The whole system is flooded and as a result a short period of euphoria sets in. That has consequences: The ducts are drilled open and are not able to take on the dosage tasks. The dams are out of order and the ground, that is adjusted to a continual measured water supply dries out quickly. Logically a quick supply of water is needed, which the arid soil can only absorb to a limited degree. The viscous circle is closed.
There is no way back. Principally this is how it works with every drug. Including crystal, cocaine, heroin and nicotine.
Now the good message: Our body can repair itself. Cells are constantly dying off and being replaced by others. The blueprint of a cell is luckily pretty stable but that takes time… and the absence of terror systems. But nothing is guaranteed.