I stop, wait until I can breathe, then ride again. If it's that steep, it takes a while to recover, even walking. Walking gives me a sense of defeat, recovering to ride again makes me feel like I conquered the hill.

If you have trouble getting started again, ride crosswise or slightly downhill until you get going.

It doesn't take very long, maybe only a minute, to lower your heatrate enough to continue on.

I usually get out of breath long before I feel lactic acid build up, on a hill.

Nanci