Love in "The Sun Rising" is immediate and romantic; remember, he is writing this just as he is waking up with his beloved. It's also the sort of love that makes you feel invincible, like you could throw down with an MMA champ or the Hulk. After all, we're talking about the kind of love that makes the speaker feel like he can pick a fight with the sun. The dude literally thinks that he and his lover are the center of the universe.
The speaker's brazen attitude about his love shows that it is a feverish, immature sort of love.
The speaker has allowed love to shut off his ability to see anything else in the world. That might sound romantic, but it's not a sustainable way to live.