I shoulda stayed in bed

I shoulda stayed in bed

I should not have bothered doing this because it wasn't worth the time or effort. "Shoulda" is a colloquial shortening of "should have." Primarily heard in US. We got trounced at our football game this morning—I shoulda just stayed in bed. A: "So, what did you think of the opera, Dad?" B: "Eh, waste of a Sunday if you ask me. I shoulda stayed in bed."
See also: bed, shoulda, stay