Many Christians receive a call from God to take up a particular ministry, but refuse to enact it. Or, by looking only at their own lives, they misinterpret such a call and ‘miss’ it. Either way, God may not repeat the call for some time, if at all, for his own purposes, and so that person will not know the blessings associated with his or her ministry.
Every one of us has a ministry of some kind or other, some more vocal or physically active than others, ranging from private prayer for the saints and various ministries to preaching, witnessing, or supporting others financially or otherwise. There are no back-seat drivers or silent partners!