I honestly believe, in this life, you need a constant. Something you can hold on to when it seems like everything else is slipping out of your control. (Sidenote: In LOST, Season 4, Episode 5 entitled "The Constant", *spoiler alert!* having Penny as his constant person that bridges across his time traveling years literally saves Desmond's life. Yes, I loved that show, too. In its prime. But back to my point.) When people fail you - as they often will because they are only human like you; when processes fail you - like applying to schools with the best laid plans and getting flat out rejected; even when you feel like you're failing yourself: the one thing you can be sure will not fail you is that incomprehensible, unconditional love.
Now, the artists does note that this type of unconditional love can also be attributed to a significant other, as he also considers his wife to be the theme of this song. But, as for me, for now, it refers to God's love. I'm not saying that now I feel like I have all the answers to every single issue I will ever face, and I'll never ever doubt anything ever again. I'm not sure I could ever really make such claims! But, I'm just saying it's comforting that there is something constant I can rely on when I experience rough patches in life. I hope you have a constant, too. =)
"All I know at the end of the day is Your love remains"
Also, I just really like this picture of sunset...