Are people who don't believe in God, pessimists?

Most certainly not, we are just Realists. There is no proof any of thousands of gods exist. I do not choose to believe or not believe. I look at the evidence, and there is none in favour of any gods. The genuine evidence shows gods are imaginary.

Nope. I'm a very positive person actually. I always try to find the good in life, even when things are going badly. So, your premise is false.

I simply don't believe an invisible wizard exists. This is not because I'm pessimistic; it's because you (or anyone else) have not given me a good reason to do so.

It's like saying that the people who don't believe in Santa are just pessimistic. Nope, it's all about the whole "no evidence" thing.

Some, but not all.

Optimism and pessimism seem to be an in-born personality trait.

No, it isn't pessimism that leads people to conclude that impossible beings don't really exist.

You are cherry-picking your data. For one thing, how do YOU know the stance toward belief of every person you've ever encountered? For another, have you ever really TRIED to accurately collect all the data available to you? Or do you ONLY notice non-believing pessimists and believing optimists?

The FACT is that, of the many, many atheists I've ever known, most were optimists.

Not believing in the supernatural does not define me. I'm quite the optimist actually.

"I find that non-believers often look at the negative and therefore will not believe." -- No, you WANT that to be true so you choose to believe it. Most atheists know that this life is all we get and try to make the most they can of it.

That is a very foolish question to be honest. My mother doesn't believe and she is the most optimistic person I have ever met. It's really a large over generalization. It would be like me saying that all those who believe in God are weak minded and easy to control.

Are you sure you don't just think they are negative because they don't agree with you?

I mean, if I walked into a pre-school and said "who's for eating plates of broccoli!", I might think that four year olds were a pessimistic bunch, judging them only from that.

No. I just go with the evidence. I actually am quite optimistic and take on challenges rather than sitting back and complaining how it will never work. Optimism/pessimism doesn't seem linked to belief in my experience. It might be though. If I was interested enough (I'm not) I would research that.

Just because I can see the negative doesn't make me a pessimist. I also see the positive.

Are you 12? What's with the random comma in your question? Go back to school.

If you mean non believers are realists, and don't spend their lives hoping for things, then yeah, that's generally the case.