Just be honest and try to be halfway sure, of what you are doing. For example, if you do not see any future, I would not bother. If you prefer to keep him as a friend, be sure, what path you choose, because he might choose to distance himself from you, to not give you hopes or to not complicate something or to not hurt somebody else by hanging with you. But do not talk yourself down, he decides, whether you are attractive enough, not you. It is good to be careful and considerate (prevents you from getting into stupid situations), but you do not need to be anxious or shy, because that will hold you back.