I'm a software engineer from India.
Recently, I suffered a personal loss which made me sad. I usually have my spirits up, but this time I just didn't feel like laughing at every stupid joke in the team meetings and so on.
It should be noted that my work didn't suffer. I did the tasks assigned to me. I met the deadlines. I didn't have even a minor spat with a coworker. I was professional, civil and polite the whole time.
My manager had a talk with me. Told me that my behavior seemed off. I told her it was because I was going through I bad time. I couldn't tell her the reason, so I just said it was personal. In her words I wasn't "energetic enough." Soon, other team members pointed it out too.
When the time for performance review came, I got a bad one. I should mention that I was repeatedly told by this manager and the previous one that I was doing extremely well, before I started acting different. I'm sure this issue is the reason for it.
Now, I'm moving to a new company. My question is this: Is it necessary/advisable for you to feign happiness in order to fit in? If you are genuinely unhappy, is it necessary to actively participate in jokes even though you may not feel like it? Shouldn't doing your job right be enough?
EDIT: The easy answer here is to not let your emotions show and act normal. But I'd like some advice on how to deal with your superiors and colleagues on the days you can't bring yourself to do that. Suppose you've lost a loved one. Something just doesn't seem right to go about your day pretending nothing happened. And it could be possible that you don't wanna talk about it. How do you deal with people in your workplace then?
FURTHER EDIT: Since a lot of people wanna know about the exact conversation I had with my manager, I'll try to recreate it:
Manager: "So, Snowman, Me and some of the other people have noticed that you're not as energetic as before and your performance is deteriorating."
Me: "I'm sorry about that, but I'm still finishing my work on time."
"Yeah, but earlier you delivered before the deadline. What's the problem?"
"It's personal and I don't wanna talk about it."
"Are you not happy with the project? Did someone say something to you?"
"No, the project is good and my colleagues are great."
"Did something happen?"
"Yes, but it's personal and I'm working hard to get past it."
"Well, from tomorrow, I wanna see the old Snowman, full of energy."
"You shouldn't say 'I'll try'. When someone asks you to do something, you should say 'I'll do it' " (spoken with a big smile, I'm silent. Meeting ends.)
It's not an exact transcript and a bit shortened, but it's close.