Paul was told, it was in his time of weakness, that God's strength is revealed. When we feel we cannot go any further, push any harder, that is where God can use us best. Especially, if we continue our focus on Him and His power in our lives, and not focus on our circumstances! Jesus told Paul that His strength was made perfect in weakness.
Paul understood at that point how God could use him completely. Paul had to surrender all himself, and realize that God can and will use any situation to His glory. Paul found release and contentment in this, as we see by his response in II Cor. 12:10-Therefore I take pleasure in infirmities, in reproaches, in needs, in persecutions, in distresses, for Christ's sake. For when I am weak, then I am strong.
Why? Because he became completely dependent upon God for all his resources, for all his needs. How about us? Where do we seek our resources to accomplish the things for God we would like? Is it in our all for Him, or His all in us? There is a difference for sure! Sometimes when we are giving our all for Jesus, we tend to do a whole lot on our own, and when we get to the burnout place in ministry we become defeated.
When we come to this place, that is where we can be the most use to God, if we surrender and humble ourselves. If we come to the throne of grace, and seek mercy, we will find exactly, the help at just the right time of need. When we truly come to the place when we understand, that His grace is sufficient for us, then we will be able to do all things through Christ who strengthens us!