I was dating an asshole yrs ago. He was 28, I was 18. He got a HUGE tattoo with my name wrapping around his arm, from wrist to bicep. I got a small facsimile, 2inch by 2inches on my arm with his name in it. Two days after breaking up (we were together for 2yrs) I had his name covered up so well you can't even tell it was a name.
I agree that it is romantic as hell, but unfortunately, we can't tell the future. You don't want something you have on your body permanently to be a regret. If you decide to get it done by a really good artist, it will not be cheap. I don't know what the prices are for tattoo artists in the states, but a really good artist charges $150per hour. So if you want a tattoo across your chest, you are probably looking at a minimum of a 3hr sitting and depending how intricate your design is, you may be paying a lot of money for even more sittings.
If things don't work out, not only are you going to feel and look like an idiot, you will be out the money for the tattoo and whatever it is going to cost for a cover-up or for it to be lasered off.