You do ego lift. You cure all your problems by taking a plate off. You did 280 before, maybe it's only 278 today. It might be 350 next week. Even the most educated and equipped trainer can't predict perfectly how capable your muscles will be day to day and successful training works with what you can do that day, not what you think you should or want to do to fend off sneering and laughing. I say you ego lift because you made it about them, not about you.
Failing is good because you know you're reaching your limits and aiming to surpass them. Sometimes the level at which you surpass won't be as broad as other times. If 280 was your PR, put on 3lb plates and try for 286. When you realize that's too easy, got for 5s, 10s, 25s, another 45, etc. You'll find PRs breaking all over the place when you discover you can lift more than you thought you could. Not when you think you should lift more than you can.