4ll39vutgiaa Getting the Discovery traits to swap is pretty hard. A lot is timing, I think. I also think you have to already have all 3 additional trait slots taken. I get Cheerful to come up a lot, but it seems to always be when I am filling the initial 3 extra slots. I have noticed that it takes max friendship with more than one sim to trigger Cheerful. That's one of the easiest to trigger for me. It also helps to have the Incredibly Friendly and/or Inspired Explorer buyable reward traits.
Hope this helps.
