First... your comment... "I had a great harvest but...." Let's just redo the sentence structure, shall we?

"I had a great harvest!"

See, much better, you were successful!

There are many reasons for short-lived crops. Some are pest and disease controls, others are just plant-specific issues, and some are the practices of the gardener.

I would just, once again, focus on your success, and keep learning. One simple way for a novice gardener (and, well, even the most seasoned pros) to lengthen their harvest is through succession planting.

A quick forum search will bring-up tons of information. Basically though, it's staggered planting over time. It works very well for both small and large areas. The only real thing to keep in mind, is the over-all preferences of the specific crop.

For example, you can succession plant spinach, lettuce, radish, etc... all through the spring, but once the weather begins to heat up, all the staggered planting in the world will not bring you more in that season. You can find other tricks like using the shade of lusher plants for extending the season of those cooler weather crops.

Anyway, that's a good place to begin. Keep learning. And remember, even the best gardeners will have complete failures. Just brush the dirt off your pants and keep going!

I wanted to give it a day to see if anyone else would comment, but this particular forum doesn't get much traffic. You could cross post in the more heavily followed Growing Tomatoes forum, or since it is about more than tomatoes, try Vegetable Gardening