Anything that lasts to eternity has to be from God; He is the true eternal One. When He does a work in us, it is actually supernatural because man cannot reproduce it. The greatest miracle is not healing the sick or even raising the dead because all these people die at the end, but those who loved to sin beginning to hate it, those who loved only themselves beginning to love God and other people, and carrying this life into eternity. Only God can do this, and no amount of human learning, skill or experience can manage to produce such miracles.
Those who serve God by ministering to people, whether it is through evangelism, teaching or any other ministry, ultimately come to recognise that God's work is God's work and we cannot accomplish it without Him. One may have the best of knowledge in one's area of work, may have developed great skills in doing it through years of experience, may have the latest technical support, may employ the best psychological tools to influence people and may use the most successful marketing strategies known to man. But all this cannot move the person we are ministering to one bit if God is not working through us (many times in spite of us). "'Not by might nor by power, but by My Spirit,' says the Lord of hosts" (Zec.4:6).
It is not that we don't need to get prepared through learning, getting trained and developing expertise. But our dependence cannot be on such things. If we have all this and more, but God is not with us, nothing lasting can come from all our efforts, even though we might dazzle undiscerning people with our cleverness and abilities! This is one of the greatest practical lessons the Lord teaches us.
Whatever our line of work is, we need to learn to depend more and more on the Holy Spirit to work in us and through us. Nothing of any real significance can be accomplished otherwise. However much knowledge, skills or experience we have, we have absolutely no ability within ourselves to transform another person's thinking or behaviour that will make them a little closer to God and a little more like Jesus. But that transformation is what they really need! The best thing we can do is to make ourselves available to the Holy Spirit as a channel He can work through. Then His work will be supernatural, much beyond what we could have imagined.
Our knowledge, training and experience can be useful to the Holy Spirit to work through us; we are not to neglect them. But our dependence on the Holy Spirit must be deep and genuine, touching every aspect of our ministry. We must also be clear in our mind not to accept any glory for ourselves but recognise in the depth of our heart that it is all by His power and might, not ours.
It is only too easy for even the best of us to slip away from our dependence on God and begin to trust in ourselves. That will be our downfall. It has happened to many of God's servants and that is what we need to watch out against.