Not only do I like this quote because it focuses forward rather than backward, but also because of the use of "fighting" and "building."
Looking back at the old vs. looking forward to the new
Looking back is, of course, a necessary part of life. It helps us learn from our mistakes, allows us to remember things we did right, and so on. But, too much looking back trips you up as you try to move forward. The best way to make an incremental improvement, but not to truly be innovative, is to focus on what already is or was. By reframing and falling in love with the problem (a necessity of good design thinking), a problem that real people have (a necessity for any human-centered design methodology), you have to stop looking back at "the way we've always done it" and instead look forward to something new that you may have never done before.
Fighting your weaknesses vs. building on your strengths
I think that often, when we try to solve a problem, or even when we just acknowledge that something is wrong and that there may be a problem, we start fighting. We fight to justify what we've done, to not look wrong, to not feel like we've made a mistake. It takes guts to acknowledge you messed up or did something that wasn't successful, but that's what it takes to move forward and start building.
In order for each of us to build a happy and successful future, we need to focus and build on our strengths. While you may have a weakness that you really need to improve, if you focus more on your weaknesses than your strengths, you'll be exhausted and frustrated trying to do it all. If you instead focus on your strengths and try to build a life and career around them, you'll find more enjoyment, success, and fulfillment. So, what happens when you run into a weakness? Decide if it's something you really need to get better at (dig deep and be honest with yourself). If not, try to delegate to someone else who is strong in that area, or find a creative way around it yourself.