In the process of preaching the gospel, every Christian plays a part. Some of us sow seeds. Others of us water seeds that have already been sown. And still others have the privilege of reaping the seeds that have already been sown and watered.
The Apostle Paul put it this way in 1 Corinthians 3:6–8,
I planted, Apollos watered, but God gave the increase. So then neither he who plants is anything, nor he who waters, but God who gives the increase. Now he who plants and he who waters are one, and each one will receive his own reward according to his own labor.
So we just don't know what's going to happen when we are sowing the seeds of the gospel. Sometimes if we don't see immediate results we grow frustrated. We think it is not working. God is not blessing. You just hang on, Christian. It ain't over 'till it's over. That seed that you have sown today may not be reaped in your lifetime. It may grow after you are in Heaven. That's when that non-Christian that you loved and nurtured and shared the gospel with will come to faith. Then again, he or she might come to faith tomorrow.
So what is our responsibility? It is to sow the seed. It is to do our part and leave the results up to God.