Bright and cheery despite when it's gloomy and weary for your sims! These sims are optimists, hence the trait name of optimist, and will act accordingly. They build relationships with other sims faster and tend to be social butterflies so make sure they've got plenty of friends! This trait mixes the cheerful trait with the happy and energized whims so your sims are always ready to be the new annoyingly bright thing next to the sun itself! They may want to hug other sims, tell jokes, and constantly meet new sims.
"These sims are half empty"
Last name "Downer", first name "Debbie"--that's how most sims would describe sims with the cynical trait. If you've ever wanted to darken every day in your sims life with a shadow of gloom and a hint of anger at the loss of faith in sim-kind, then look no further! The cynical trait blends a little bit of anger with a tad of boredom and the gloomy trait so they'll always be the wet blanket at your next get together! Their social needs decay slower because they have a harder time making friends (mostly because they kick trash in their free time), so your social recluse is available on even the sunniest of days.
Neither trait should interfere with existing mods or game defaults.