There is transient depression as we heal. For no reason, you might wake up depressed, or have it descend upon you.
It's important to know it's temporary and has a physical derivation caused by fluctuating hormones released from your fat as you lose weight, or as a result of anesthesia and having someone inside you messing with your guts. (Your guts produce neurohormones that regulate mood.)
Hang in there. Deep breathe, drink LOTS of water, do comedy therapy on Netflix, walk a LOT, get outside into sunshine and nature, hug someone hard for a long time! Smile to your reflection in the mirror, get enough sleep, eat your protein and veg and all will be well in your world soon.