(J.R. Miller, "Help for the Day")
When we are strong, or deem ourselves strong — we are really weak, since then we trust in ourselves, and do not seek Divine help. But when we are consciously weak, knowing ourselves unequal to our duties and struggles — we are strong, because then we turn to Christ and get His strength.
Too many people think that their weakness is a barrier to their usefulness, or make it an excuse for doing little with their life. Instead of this, however, if we trust Christ, He will transform our weakness into strength. He says His strength is made perfect in weakness; that is, what is lacking in human strength, He fills and makes up with Divine strength.
Paul had learned this when he said he gloried now in his weaknesses, because on account of them the strength of Christ rested upon him — so that when he was weak, then he was strong.
"But He said to me, 'My grace is sufficient for you, for My power is made perfect in weakness.' Therefore I will boast all the more gladly about my weaknesses, so that Christ's power may rest on me. That is why, for Christ's sake, I delight in weaknesses, in insults, in hardships, in persecutions, in difficulties. For when I am weak, then I am strong!" 2 Corinthians 12:9-10