Whole-heartedly is very hard. Just reading Evangelism and the Sovereignty of God by J.I. Packer.
“We shall not inquire anxiously after the minimum outlay of effort in evangelism that will satisfy God. But we shall ask eagerly, and pray earnestly to be shown, just how much it is in our power to do to spread the knowledge of Christ among men; and once we see what the possibilites are, we shall give ourselves whole-heartedly to the task.”
I agree. Much prayer is needed.