You can always do it again in the future! Additionally, you don't know how strong the dose even is, how much you need, how you will react, etc. Back in the days of Sunshine, an occasional user could take an eighth of a tab and get off, while other people would drop two whole tabs. I had other types of tabs, years ago, that were scored with an indented line on them - and not for nothing!

Don't get me wrong, I'm not against taking a few hundred mics, but you usually don't need that much the first time - and will probably be very happy with the experience you have. Just keep some smoke around and you'll be fine.
Better to overestimate the potencey, IMO, than the opposite.