You're at a bar where people are dancing. Your friend invites you to dance, but you don't want to dance because you don't like the song that's playing. You say:
I think I'll sit this one out.
Use this expression to announce something that you've just decided to do:
I think I'll take a shower.
I think I'll work from home today.
This phrase comes from sports. When you "sit out" a game or a match, you sit outside of the court or field. So sitting something out means that you do not participate.
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