Term for figure of speech in: 'Life is awesome, I confess'
There might be something even more specific lurking out there, but I think it's acceptable to just call this juxtaposition, maybe even a loose form of oxymoron. You're placing two contrasting things next to each other for literary effect.
Accusations and confessions carry a negative connotation. Both imply that there was some conflict or wrongdoing. But "life is awesome" is obviously a positive statement, and though the grand vision itself could be something wicked, "grand" is typically a positive term.
https://www.litcharts.com/literary-devices-and-terms/juxtaposition