Stop thinking too hard about stuff that doesn't matter

I am driving myself and my friends crazy with this. I cannot seem to stop over analyzing everything that happens in my life. It effects my ability to make decisions and when I finally do make one I question myself afterwards, often leading to regrets. Everyday is consumed with feelings that I made the wrong choices, even though I KNOW it was the right one. I have sabotaged many relationships due to over thinking and trying to imagine what the other person must/could have meant by their actions or words.. instead of just accepting it for face value I feel compelled to think it over and over and over again. How do I put this to rest?!