Being vulnerable definitely isn't easy. It can be downright scary! To allow yourself to experience relationships and intimacy and be silly can be risky . . . and amazingly rewarding. You can go the route of being cool and not taking risks or being silly, but how much fulfillment will you really get out of life?
If we don't allow ourselves to be vulnerable, we limit ourselves. We don't get as much out of our relationships, we feel less fulfilled, and risk our relationships being superficial.
Do you crave aunthenticity in your life? Start by being authentic yourself and letting people know how you feel. I've done this and it can be very liberating. It usually can start with an "I statement." I know it sounds corny and cliche, but it can be relieving to just say how we feel.