I have more of a problem with hiding my emotions than showing them. This especially occurs with happiness, sadness, and amusement. If something tragic affects me, I can easily become a crybaby. When I feel good, I can't help but smile. If something odd or funny happens, I have a hard time preventing myself from laughing--even if it's just a snicker. Sometimes--especially in the last case--that comes by as rather rude or mean, but...
Anger is something I tend to compromise with rather than bottle up or express... and besides, I only express anger with objects, not people...
As for love... I think that's the only emotion I can suppress when I feel it for a real person. Of course, I hardly ever feel that emotion in that situation, so how would I know... However, I have a hard time hiding love for a fictional character, specifically one of my creation...