This is a man telling a girl that he'll "never stop" protecting, taking pride in, providing for, and ultimately, loving her. He's basically telling her that no other woman can touch his heart because it is so wrapped up in feelings for her. He's saying that when they're old or when her hair falls out of when she's sick or when she's not the prettiest or just not at her best, that won'y change his great love for her. It seems to be a wedding or marriage song (especially the "wedding version"). When he says (or rather, sings) the line, "I will never get used to you," he's telling her that she isn't going to get old or boring, that everyday will ignite a new fire of love for her, that everyday he will wake, just as in love with her as the day he wrote the song.
This is the ultimate love song.
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