I just failed my promo series to Gold for the 6th time.

You should just "carry harder".

But in all honestly, as someone that has just recently been bumped to gold, it is just luck. Obviously you are good enough if you keep getting into the promos, so just keep trying until you can get lucky enough not to have a feeding team so you can win 4/6 games.

So frustrated. Am I doing something wrong or should I just keep trying?

Yes.

Next time you're in your promos, dont play ranked after you lose a promo match, this helps because A. there is a chance that you might the same trash teammate again B. It would help you get off tilt, play another game, single player game, so you can't frustrate yourself over anothers shortcomings (Skyrim is my goto)

dude i know exactly how you feel. I just cant get it up. 'meaning my lp' i keep winning 1-2 then losing 1-2 then winning until im 1 win away from promos then start it all over again.