You are probably right. But optimism and pessimism are on a sliding scale. You may be more on the optimistic side, but it is very likely you have some pessimism still lurking in your mind. And if you don't right now, you may tomorrow, because the world, your own brain, the media, and communication in general all function as if they had a negative bias, and if you don't know how to protect yourself, that negativity will worm its way into your mind, ruining a little motivation here, spoiling a little good feeling there, and establishing an outpost of pessimism in your mind — an outpost that will grow if you don't crush it.
Pessimism is insidious. It sneaks into your mind against your will, bringing you down and making you feel bad unnecessarily. You have the tools here to protect yourself and raise your mood.
Probably the best way to use this site would be to wait until you feel down. When you feel discouraged or disheartened, browse around this site. The first, best place to go is Crush Pessimism. Do the writing exercise, and if you still feel disheartened the next day, do it again. And every day until you feel better.
If you have a friend and you want to share this site with her or him, but you feel sure s/he would take offense because s/he might think, "I'm not a pessimist," send this post first. Many people don't know enough about optimism and pessimism to know that it is not a matter of being one or the other. Almost everybody is somewhere between those two extremes, which also means almost everybody can move themselves a little higher, and doing so will improve their health, their mood, their productivity, and and their motivation.