I have to go do something
A cowardly way to leave someone when things get serious. It's like hiding from a math test.
'I have to go do something.' He left me mid-kiss like I was a bad flavor of candy.
'I have to go do something.' She vanished during our third song like I was a broken beat.
'I have to go do something.' He left me in the middle of a conversation like I was a broken phone.