What's the biggest mistake that actually made you a better gardener?

One of my biggest gardening mistakes was planting my first vegetable garden far too early because I got excited by a few warm spring days. I hadn't paid enough attention to the average last frost date, and one cold night wiped out almost everything I'd planted. It was a frustrating lesson, but it taught me to respect my local climate and be a lot more patient. What's the biggest mistake you've made in the garden that ended up teaching you the most?

My biggest mistake was letting ants destroy my whole purple hull pea harvest.

I now know I could have killed them with vinegar (or used dishwater) and saved the harvest.

Mine was more a stroke of luck. We have a garden tractor with a tiller attachment that would not start a few years ago. This led me to a minimum tillage, soil building method of gardening and the results have been fantastic. I now do cover crops between plants and rows and build soil. Churning soil into a fine powder with a tiller is the worst thing possible, the garden tractor sits quietly today.