Once when I was twelve, I told a girl I loved her over the interwebs. I had maybe said 3 sentences to her in real life. She said she loved me back. I was twelve.
Then when I was sixteen. I had been dating a girl for about a week who I had liked for a good year before that. We fooled around, and I had been starting to think that I was taking advantage of her (first girl I made out with) and she told me she loved me over a text message. After less than a week of dating (for emphasis).
I did the ever so suave and romantic "thanks" and of course I got back "that's it?" I then told her, "Yeah, me too". Lying to a girl that you love her is a very hard thing to do.
After that, I began to seriously reconsider that particular relationship and broke it off with her a week later. I felt proud of myself, because she offered to have sex with me before I broke it off.
A year later, I got handjob from said girl. I then felt obligated to help her run away from her parents. Nearly was arrested. 2 years later (present), she is now dating my best friend. She is legally insane, apparently. I really do want to tell my friend that there is a good chance she is using him (tried banging my other friend to annoy me), but i cant bring myself to do it.
Also two years ago I got into what I considered my first real relationship. It lasted to months, I got a little too tipsy on New years and told her "Happy New Years, Love ya lots" (She took it as, "I love you", when in reality I didn't actually think I had said anything to crazy). She said she loved me back, but I didn't mind to much. I really liked this girl, so I kind of just let it pass, careful not to say it again. 6 months later, shit hit the fan. She kind of held that against me, got her friends to turn on me, and ended it. There is a lot more to that story, most of it realistically her fault, but I would rather just not bring up that particular instance. It still makes me rage to this day.
So yeah, I have been very careful with my relationships since then. Mostly too careful (didn't make my move and sure enough someone else swooped in), but careful nonetheless. Last year I was pretty dejected from relationships. I had a short little skirmish with the crazy girl, another week long relationship with someone I had yet again taken advantage of, so I basically decided it wasn't for me. I've gotten loads better though.