I don't know who said that, but I think it's important to remember. One of the hardest parts of living the Christian life is dealing with constant failure. "Oops, I did it again" is not just a Brittany Spears song. We want to feel we are making progress, but then we go to Confession, squirm at little, and say: "Um, pretty much the same as last month." (No, that doesn't work--you have to say your sins. Sorry!)
It's hard. But persistence is so crucial! (And it's not like God isn't helping. He is. More than we know or realize.)
I usually invoke the Pathetic Principle. It goes something like this: "See, God, I totally screwed up at the slightest provocation. Clearly, I am pathetic. I need more grace. Lots more. You're pretty much going to have to pick me up and carry me because I've met rocks with more will power." Then He says something along the lines of, "Ok, my beloved one, but let's try and do things my way instead of your way for a change...."
We want to avoid two extremes reactions to sin:
One extreme: "Meh. Oh well."
The other extreme: "I give up. I am never going to be a decent human being, let alone a good Christian."
I know I am weak and I don't pray enough, so why am I surprised when I sin? I try to embrace the humility that comes from knowing I'm a sinner, gratefully embrace the love and forgiveness God gives me, and then move on. When you sin, don't be surprised, don't be blasé', don't be discouraged, and don't dwell on it once you have been forgiven.
Here is the story of a St. Hyacintha, a saint who kept falling off the bandwagon just like we do.