Consider the lilies of the field, how they grow, they simply are! Think of the sea, the air, the sun, the stars and the moon – all these are, and what a ministration they exert. So often we mar God’s designed influence through us by our self-conscious effort to be consistent and useful. Jesus says that there is only one way to develop spiritually, and that is by concentration on God. "Do not bother about being of use to others; believe on Me" – pay attention to the Source, and out of you will flow rivers of living water. We cannot get at the springs of our natural life by common sense, and Jesus is teaching that growth in spiritual life does not depend on our watching it, but on concentration on our Father in heaven. Our heavenly Father knows the circumstances we are in, and if we keep concentrated on Him we will grow spiritually as the lilies.
The people who influence us most are not those who buttonhole us and talk to us, but those who live their lives like the stars in heaven and the lilies in the field, perfectly simply and unaffectedly. Those are the lives that mould us.
If you want to be of use to God, get rightly related to Jesus Christ and He will make you of use unconsciously every minute you live.