This is interesting. I like how light and simple it is; like if it was something concrete, you could pick it up with a couple of fingers and place it on the wind, or something like that :)
There are a few things I'd like to persnicket at though, just to make it more readable. First is the full stop in the middle of the poem. When reading, this kind of creates a stop that may not be the type of stop you're looking for to precede the 'But'. I personally find the full stop too heavy and invasive; an extra line break I think would give the effect that you're looking for without adding too much weight when the reader comes to that stop.
I think the 'But' works well on a line by itself. The line break gives some time to turn the poem onto the positives. It took me some thinking to understand the importance of the 'But' though. Because a but connects contrasting statements, ideas, etc., I didn't see how a but would fit in this poem. My reasoning for this was that the three objects and ideas in the first part of the poem ('Your eyes...', 'Your smile...' and 'Your lips...') could very well be viewed in a positive light and that this would pose no contrast to the second part of the poem. But after reading through a few times, I can now see how the second part of the poem can use a but to contrast the freeing effect of the subject's love on the narrator with awing effect of the subject's features on the narrator in the first part of the poem. I would say that this poem would be just another poem without its 'But'.
A couple things concerning grammar and spelling should also be mentioned. It would be interesting if smiles stoped peoples hearts -- and maybe some do -- but I don't believe that was your intention? Also, you used the singular verb 'Makes' to follow the plural noun 'lips'; it should 'Make' if you want to be correct, but if you don't want to be correct that's alright, it just wouldn't be consistent with your correct usage of a plural verb after 'eyes'.
One last thing: I enjoy the 'ee' sounds at the end of the poem. I'm not quite sure what it is but there's something about the last line that doesn't quite fit. I know it reinforces what was said earlier because it repeats the exact same words, but I feel it needs a more submissive verb. This is because you write 'Makes' to start, which I think is suitable there because it would shake anything that was oppressing your freedom, and then write 'Allows' next, which fits nicely because it reinforces the idea of freedom as it is quite a soft word, but then revisit 'Makes' to finish, which goes back to a stronger more directive verb and kind of implies that you're being pushed around. I don't think it's a nice place to end because it doesn't sit with the poem. I think you should consider replacing it with a verb that is similar to 'Allows'.
Well! That's all I have to say. I hope my legalistic approach didn't frighten you away from writing poetry. I can see that freedom of the pen (or keyboard ) in your writing and sometimes any formal approaches can ruin that freedom. I just hope that you'll consider these suggestions and hopefully improve your writing.