Hope your first day went ok, sometimes worriyng about things beforehand make things seem worse that what they actually turn out. Also, i think if you have not been used to mixing much with people in a work environment much recently, since you gave up your job, you lose the social skills of chatting and just generally getting along with others, especially people you are meeting for the first time.
You are so young with so many options, look around - you may see something else you could see yourself doing to earn your crusts....