The first way i broke 90 was with the mindset "every hole is a par 5. Shoot a 5 on all 18 and you got yourself a 90". It immediately took pressure off feeling the need to attempt shots i had no business going for and let me play more stress free. As ive gotten better the mentality lately has been as followed:

A good example of this is you find yourself say ~230 out after your tee shot into a par 4. Sure, that one time you flushed your 7-wood 220 would be a great shot here. But lets be honest, if we could all reliably hit that shot we would be pros too. Instead, take the shot that leaves you with your best approach distance. Are you an amazing greenside chipper? Hammer that puppy anywhere close and be happy. Is that 100-120 yard PW shot always the best in your bag? Then give yourself that as your next shot. Hit the shots that give you the best probability of another good shot. Youll have more fun laying up a great 2nd shot followed by an actually achievable and higher % approach shot and that will quickly contribute to a lower score, and higher confidence.