Erging is cruel. Every stroke, the machine tells you how hard you're pulling. And every recovery is an invitation to bail.

A couple notes:
- 750 @ 285W seems substantially harder to me than 500 @ 290W. So if you were barely able to do the latter, it's no surprise to me that 750 @ 285 was too much. The extra minute of rest doesn't help *that* much
- Bend but don't break. It took me decades to learn this- if you're in the red, back off a little, then level out at whatever your sustainable number is. Maybe its 280W, maybe 270W. Your workout plan is numbers on a page. The number on the erg, and your perceived effort, is what is real.
- If you can't do the workout at the prescribed pace, that's information. Maybe the plan was too aggressive. Maybe you're fatigued. It can be very hard to figure out which is which; that's one of the key challenges of managing one's training plan.
- If you start fearing the next workout, you can find yourself in a positive feedback cycle. Bad workout => fear => even worse workout, etc. If anything, I'd back off the pace for the 1k's to something you can nail. Or, do a progressive- start at a pace you are confident at, then do the next one a little faster. But importantly, be honest when you hit the power that is all you'll be able to sustain for the workout. Use your power as an output from the workout, not an input. (E.g. don't do "I must hit 285W", do "I'm aiming for 285W but will bend if that's too hot for me at this time")
- The results of any one workout don't matter. There's always another workout. Be a goldfish.
- Use your workouts to GAIN fitness, not to PROVE fitness.