The speaker is a loving yet realistic man. He doesn't tell his beloved that he's the most amazing person to ever live. He knows that no one is perfect, but finds his lover beautiful in spite of his mortality and flaws. He may seem like kind of a downer at times, but we could also see him as incredibly truthful. He acknowledges that life is fleeting, and wants to make the most of it. His lack of religious belief might even be what inspires him to "find the mortal world enough." For the speaker, nothing lasts forever, and that's what makes life beautiful.