"...for my power is made perfect in weakness" - One of my favourite quotes, and I'm not even a Christian (not really I don't think).
I think I understand this passage. Grace, being divine favour, more than compensates for any of the weaknesses that we, as "the children of men", have to endure, and we shouldn't seek power either for its own sake or in order to attain some other goal in life. "Weakness" often isn't as it seems, and one of our goals in life should be to renounce our futile attempts to gain some sort of mastery over nature and the circumstances we may happen to find ourselves in.