We are afraid of what people will think or we fear that it might be inappropriate or it just doesn't "feel" right. So we go to movies and read books and attend sporting events and watch concerts and we let ourselves go. We watch people live passionate lives and instinctively we think, "That's living!" Society seems more accepting of emotions in any of the above circumstances, but if a guy lets out "Wahoooo!" in the office after getting a promotion or if a writer does a literal "happy dance" after getting a book contract, people think they are crazy.
I was drawn to writing and music in my late teens. I'd always been known as the shy guy. But writing and music gave me an outlet to express myself. I felt alive while in those venues and I knew that I had to have both in my life. Sometimes I even chose them over people. Those aren't some of my proudest moments, but it's the truth. Unfortunately, it shows the extent that some of us are willing to go to in order to feel alive.
Recognizing this has helped me to show more emotion when the situation warrants it. Nobody is ever going to accuse me of being Mr. Outgoing, but I'm guessing I won't be compared to the Tin Man anytime soon either.