Former bantamweight champion  Aljamain Sterling made his featherweight debut at UFC 300 against eighth-ranked  Calvin Kattar .  If he had lost, Sterling may have retired. “Fight day in the backroom is when I really started to second guess a lot of everything.  I was just having doubt of like, man, if this doesn’t go well I don’t know where I go from here,” Sterling said on  The MMA Hour .  ”Do I continue to keep fighting?  Do I just call it quits kind of thing