Perfectionism, in and of itself, is a bane. So, why in the world would Paul lay this mandate on the Corinthian churches? Of course, Jesus did the same thing in Matthew 5:48, “be perfect.” It must be internal excellence then and not external behaviors.
II Corinthians 13:11b
. . . Aim for perfection, listen to my appeal, be of one mind, live in peace. And the God of love and peace will be with you.
In other words, aiming for perfection within is a good thing. And how do I do that? It’s what we’re all supposed to be about.
Christ within, the ultimate perfection, illuminating the path. Isn’t that the point? Becoming like Jesus is first and foremost about the interior life which then transforms the exterior–our behaviors respond to our thoughts and spirit. Where we make mistakes: sin, judge, and break basic commandments, we are given insight (hints) into the kind of work that must be done inside.
Until the “why” of my choices is understood and healed, my conduct will fall back to habits.
My college age daughter does not drive a car. She is afraid and anxious and these feelings override any desire she might have to learn. Something has to change within before she will make this leap. I have been saying to her to keep practicing; her fears will dissipate the more she drives. But then, she had an accident in a parking lot and before that, a tire blew out when she jumped a curb. Her practice alone is not working.
This is really no different from any of the behaviors I want to see reconstructed. I tend to judge others. Oh, I can say that I will not judge today. I will practice not judging. But what is making me judge? My own insecurities? My pride? My fear?
There is no fear in love. But perfect love drives out fear . . . [I John 4:18a]
I love the Christ whose Spirit is within me. That same Spirit of Christ is within others as well. How can I love my personal version and not the one outside myself?
Perfect: conforming to an ideal.
Meditations from Zion 
I like how that translation says “Aim” for perfection. Perfection in and of itself is not possible. We are not and cannot be perfect, in our fallen human state. We can however, aim all of our efforts in that direction, trusting God to pick us when we once again miss the mark and setting our sights back on him. When we keep our focus on Christ, we are bound to have better aim.