Maybe teaching is not for me

Someone said that they were told maybe this program was not for them. Well, maybe this is for them and not for me. I made the first F I have ever made in my life in this program this semester. I've never been the one to complain or fuss and I'm still not. Now that I've cried and pondered and cried some more. I've began to think that maybe teaching is not the field for me. I've been teaching and doing lesson plans for a year and a half. If I can't even do a lesson plan, then its obvious that I'm definitely not a good teacher. Amazingly, this is the first time that I have ever felt this way. I've always felt that this was something that I wanted to do for the rest of my life. Something that I was called to do. Maybe this is a sign that it is not. I mean if I can't do a lesson plan, then I can't possibly be an effective teacher. The lesson plan is what you follow to teach. If I'm failing my lesson plan, then I must be failing my students. This all means that the past year and a half of my life have been used to cheat someone's child out of the education that they deserve. I am a parent and I wouldn't want any teacher cheating my child. I wouldn't want him to get to the next grade and be missing something because the teacher was not effective.
Even if this program is about getting better, I've been teaching almost two years. I should know how to something as simple as a lesson plan. Since I can't, I need to go home.
I love everyone that I have met in Teacher Corps and I hope that you are all extremely successful, but I'm not sure what my next move will be. Good Luck!!! Wish me well.