The Kingdom of Heaven is not meat and drink. That said, you shouldn't feel guilty about not keeping the fast strictly, especially your first time out. As already said, fasting is something that needs to be eased into by the faithful. And if you don't couple your fasting with almsgiving and prayer, your fasting is ultimately in vain. Keep doing as you're doing and make sure that your fasting is done with the blessing of your priest. If someone offers you something that may be on the "forbidden" list, make the sign of the cross, thank them and eat joyfully.