First, I'm not entirely sure it's true that, by expecting the worst, pessimists are pleasantly surprised when things don't go so badly. It really depends on the kind of pessimist. Some people are just upset about everything, and when things go better than expected, they find something else to be upset about. Maybe that's not really pessimism. I don't know. I'm honestly not much a fan of "optimism vs. pessimism" conversations, because each one of those words can mean a lot of things, not to mention that there is middle ground between them. But if you had a battle between two robots named Optimist Prime and Pessimist Prime, I'd be all over that.
Moving on, I think I initially misinterpreted what T-Rex says in panel 6. What he is probably saying is, "If you're a pessimist, and imagining hard enough, life is going to seem so horrible that you are going to freak out over everything that happens. Like spider eggs hatching and tunneling out of your stomach." But I think that if you accompany imaginative pessimism with a good sense of humor, it makes life far more tolerable.
I've talked before about laughing at the horrible things in life. Sometimes, life is already horrible enough that you can laugh at it, because laughing at it is the only thing that keeps you from totally freaking out and totally losing your shit.
Sometimes, though, something happens that is just mildly unfortunate, and maybe a little frustrating. Nothing laugh-worthy, but you don't really want to complain about it too much, because you know some people have much more serious problems.
Like, say that you misplaced your wallet. You know it couldn't have gone far, but you just can't find it. It's got your credit card, your driver's license, and all your cash. It'll turn up eventually, but in the meantime, you are at an inconvenience. There's nothing funny about this, and it doesn't make for much conversation. "How's it going?" "Oh, dude, I can't find my wallet." "Aw, man, that sucks. Good luck finding it." "Thanks."
But let's say you let your imagination run wild thinking about what could go wrong without your wallet. Picture yourself getting pulled over and saying, "Sorry, officer, I don't have my license on me. I must have left it at the bar the other night before driving home. I was pretty wasted, y'know, so it's a miracle I even found my keys."
Or you could go the other direction, making a big deal out of something trivial in your wallet. "Oh, fuck, I can't find my wallet! And that has my portable periodic table in it! You know I can never remember the atomic number for bismuth!" (If you're wondering, it's 83.)
Use your imagination to make everything worse than it really is, because just like every mistake is a learning opportunity, every misfortune is a laughing opportunity.