
Alright, here are some of the suggestions that I have. I will add another comment for the ones that I figure out later :).
It's the summer I'm thinking of -> I'm not really sure what he means by this, but I would translate it as: 'C'est l'été dont je pense" like he is talking about a particular summer
It's just that I'm always falling -> Something about him never being enough like "falling short." This phrase of falling appears a lot in rock songs for some reason and I can never fully explain what it means. Something about "losing faith in what you thought was guaranteed / you could do."
And it makes me feel bad -> It makes him feel bad that he is always failing at reaching other people's expectations
If I saw something new
I guess I wouldn't worry
If I saw something new
I guess I wouldn't care
-> I think that all of that means that he likes how things are now (with a girlfriend, his life, or something else) that if something/somebody else came along, he wouldn't care or worry because he likes the things/people that he has right now
Said I love the way that you smile, don't -> I'm not really sure what the 'don't' means in this phrase, but I could only assume that it would mean something like "don't disagree" or "don't stop doing it" because he says after that it makes him want to watch her, so he doesn't want her to hide her smile.
This is my best bet of what the song is about. It's kind of all over the place, but if anything else doesn't make sense, I could try and decipher it for you :).
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