I think, therefore I'm single
I like this one because it describes my current situation, but I don't expect it stay true forever. This is why I don't want to get any sort of tattoo simply because I don't expect things to stay interested in everything very long.
Only visiting this planet
In the past I've often been thought of as an alien. People would look at me funny when I did something unusual or explained how I thought. It's an inside joke to just myself really, though.
Edit: He let me keep both. Cool.