A towel is the most massively useful thing an interstellar hitch hiker can have.
Partly it has practical value, you can wrap it around you for warmth, wet it for use in hand-to-hand combat, wrap it around your head to avoid the gaze of the Ravenous Bugblatter Beast of Traal or dry yourself off if it still seems clean enough.
More importantly, a towel has immense psychological value.