In D&C 88:81 the Lord commands us that we must warn our neighbor. Warn them about what? The time has come. Christ has re-established his church back upon the earth. How can we sit idle and let our friends and family not reap the blessings of the gospel? I've had friends and family who have taken the missionary discussions and although most of them have not been converted a small seed has planted which can grow if triggered by some means.
As a missionary, I will be sent out to testify and warn the people. I can be a missionary today and warn those by living my standards, being Christ-like, and serving others.