I'm a pessimist who insists on being optimistic. I... decide that life cannot be lived under a dark shadow

For a pessimist, I think that is a healthy attitude. I think some forms of pessimism can lead to depression and a lack of motivation, and that's something that should be resisted.

I seek out information that conflicts with what I think I know.

In many cases, I have to do this too, if only because as @mobbs mentioned earlier, there is no one in my immediate environment that holds an opposing opinion on a topic to debate. Or sometimes the best proponents for an idea may be people that are only indirectly accessible through their writings.

But this method is a bit inferior in some ways, because it is much easier to "win" an argument in your own mind when your own counter-arguments aren't themselves subject to dispute.

Long answer. Sorry.

There's absolutely no reason to apologize for a long answer, too me it just shows you're engaged on the topic. I do typically take longer to reply to longer messages, because I need more time to digest them and to avoid ignoring important points that were made in the message, so please don't take that amiss.