When Paul wrote, "I can do all things through Christ which strengthens me," he did not mean that he was to do all things and then rely on the Lord to find strength. He meant that for all he was told to do he could rely on the Lord to supply the strength.
God's work in the world has been hindered by our self-strengthened work. Self-driven work finally wears us thin, and we burn out. Self has driven out the Spirit, and the strength that is offered. The Holy Spirit should not only be our direction, but our strength. We are to yield to Him, and wait for the strength He supplies. We are to rest in Him.
What does it mean to rest in Him? To be still and know that He is God? Those that wait upon the Lord shall renew their strength. They shall mount up as eagles. The Lord shall be the wind beneath their wings. That wind is constant, never wavering of faltering. It is as sure as He is the cornerstone, our foundation. It supports all that you are, and in every way supplies strength for His calling, for your need, for every moment, every concern. That strength is your heartbeat, and you cannot exist without it.
When you are tired or fear suddenly closes around your heart, rest in the Lord until you are joyful again─until His strength has become your own. Let your time of rest be one where His strength is renewed. Never seek to work for Him with your own strength. Work only with Him. You will discover that constant wind that carries you in the height of the Spirit. Live with Him, and in Him, and He will open doors of His own desire. My own self can do nothing, and it is in that moment of awareness that I find Him.