How to realistically manage expectations?

I've been golfing two years and I've been improving a great deal. My goal this year is to break 90, my previous best is 92 on a par 70. Today I was playing lights out through 6 holes. Then I started hitting terrible shots and losing confidence. Finished the front 9 with double, triple, triple. Back 9 started double double and then hole 12. I toed my driver straight right and was too embarrassed to got pick up my ball. I dropped in the fairway only to top my 3 wood twice. At this point my round was over. I was defeated and I completely killed the vibes. This happens all too often where I just lose my swing, my confidence and then i give up. I really feel like I have potential and can hit all the shots needed to put together a good round but always seem to just be completely inconsistent. Anyway who wants to buy a set of JPX 925s (gently used)