It's an odd and pleasurable feeling (for most), so you'll know.

Just don't freak out. I have a friend that had to take a friend of hers to the hospital because he got high for the first time and simply couldn't take it. I guess it was too much for him? Who knows. The friend just kept saying something like "something's wrong, i need to go to the hospital".

I don't mean to scare you, but honestly, just relax and enjoy.