Not to get poetic, but true love sets a fire inside you that'll never burn out. It'll never burn out because if your partner really loves you, he/she will keep relighting that fire because it's important to them that you always feel that love.
Loving someone is the most selfless thing you can do because everything you do for them is for their happiness, not yours.
A real healthy and loving relationship looks like two people doing their best to always make sure their partner is happy and loved the way they want to be.