Hanging On To Summer

I really don't have much of a green thumb - just ask anyone, so when I have luck with something, I just have to show it off. If anyone can tell me what this flower is, great! I went nuts in the Spring planting all kinds of seeds - my idea of planting is pushing aside some dirt, throwing the seeds in, covering them up and then checking every 5 minutes to see if anything is happening. Well, this flower popped up mid-summer, just one of them and I love it (so if it's really a weed, please humor me and tell me it's something fancy!). We have these other yellow flowers growing and I was all excited until Mike told me they were weeds...I still think they are from some seeds I threw on the ground.