Made my first investment recently! 250$ into BTC, as that's all I could comfortably put into it at the moment. How do I deal with the nerves?

But I'm an absolute bundle of nerves! My friend and I are actually doing this together -- and we made the investment just a little while ago. Seeing it dip hurts, man. But I hope it ends up working out. We're currently at a loss of about 30$, last I checked. I'm only 18 - my friend is the same, which is why 250 is practically all we can do at the moment and for the foreseeable future. But seeing the money dip further and further makes it so much harder than I thought it'd be to trust it.

How do I deal with the nerves?