As you age and use more and more drugs the less euphoric they become.
That 80mg oxycontin pill you might have snorted back when you were 20 will never feel the same.
For instance I hadn't had opioids in a couple of years (having previously been a very heavy opioid user) and I got a couple real pharmaceutical 80mg oxycontin pills (not pressed).
I was pretty excited, and before a university finance lecture of all things, i snorted a whole 80mg pill, with zero tolerance (FYI please don't snort OC80s with zero tolerance -- I'm built different) and went to class. Sure it was strong and I felt pretty good but I was kind of disappointed. I expected more as I had no tolerance whatsoever. After class I snorted another one, and it just ended up making me feel nauseated more than it made me feel good.