I guess for me in my last campaign, it was less that I was trying to be a jokester and more that actions which seemed somewhat reasonable to me and high-risk/high-reward were not welcomed by the rest of the group and I didn't realize how serious people were going to be. We were playing in the world of Firefly and I tried hailing an approaching ship to see what they wanted and if I could negotiate.

The fact that the DM was shocked should have been a hint that I was doing the wrong thing, but at the time I thought that I found a plot hole and was doing such a good job that the DM was blown away. I was wrong and my character has incapacitated by another member of the crew, which continued until I realized that I probably wasn't welcome to continue campaigning with the group. When I realized this, I genuinely felt really bad that I'd probably upset the group, but it wasn't until now that I realized how seriously people take this.

I've never before played with the specific intent of keeping my character alive, but I think that was more of a videogame mentality. Other folks in the group aren't exactly excited that I'm putting their characters lives on the line because people obviously invest real time and care into this. My realization was less that I joke too much and more that I don't take things seriously enough.