How can I stop my phone from sending a text?

For about 6 months now I have had the Samsung Impression. It's a great phone and I love the keyboard and touch screen and all that jazz. But for those 6 months, I had thought that if I was sending a text and then wanted to reword or just not send it I could just end before it says "Sent" and it would be put into my outbox. And every time I did that it did go into my outbox. But as I was texting my friend and then decided to not send it, I ended it before it said "sent" and thought it was a done deal. But the text went through! Now I am horribly scared that I may have sent double messages to a lot of people or sent things on accident to people! Please tell me it was just a mistake. Or how to fix it. Thank you.