You have your towel.
You are prepared.

A towel is about the most massively useful thing an interstellar hitchhiker can have. Partly because it has great practical value — you can wrap it around you for warmth, use it to sail a miniraft, wet it for use in hand-to-hand combat, and of course dry yourself with it.

But more importantly, a towel has immense psychological value. For some reason, if a non-hitchhiker discovers that a hitchhiker has their towel with them, he will automatically assume that they are also in possession of a toothbrush, washcloth, soap, tin of biscuits, flask, compass, map, ball of string, gnat spray, wet-weather gear, and various other useful things.

Any man who can hitch the length and breadth of the galaxy, rough it, slum it, struggle against terrible odds, win through, and still knows where his towel is — is clearly a man to be reckoned with.

— Douglas Adams, The Hitchhiker's Guide to the Galaxy