system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do our bodies build up tolerances for things we may not want a tolerance to?
gpt
Your body is always trying to maintain homeostasis. 

If you start pumping a bunch of testosterone, for example, into your body, it achieves homeostasis by reducing natural testosterone production to compensate. 

If you ingest caffeine all the time, thereby blocking adenosine receptors, your body compensates by developing even more adenosine receptors.