Mac dropped "Self Care" Friday ... a single with lyrics that include, "Well, didn't know what I was missing. Now I see a lil' different. We play it cool. We know we f***ed up, yeah. You keep on sayin' you in love, so? Tell me are you really down?"

Fans and reports were quick to connect the lyrics to Mac's split with Ariana a couple months ago. However, our sources say Mac wrote, produced and completed the track last year.

As we've reported -- Ariana is engaged to SNL comedian Pete Davidson -- the two even went in on a massive NYC condo together.