At our Baptism we were all accepted as children of God and called to follow Jesus Christ as his disciples and apostles. Disciple comes from a Latin word and means someone who is learning. We learn about Jesus by following him and seeking to become more like him. Apostle comes from a Greek word meaning one who is sent out. Having learnt about Jesus we are called to go forth and tell others about Him (to evangelise).
As lay people (not consecrated or ordained) we live out our faith and give witness to Jesus in the midst of our work and daily lives with our friends and those we work with, at school and in our social lives. We do this not just by what we say, but perhaps even more by the way we act, especially towards others
If we are people of truth, love and goodness, cheerfully serving others and meeting our responsibilities without boasting or complaining, then we are witnessing to the faith that we profess.
The vocation to the Single Life may be lived out either from choice or from circumstance. Some people choose to remain single because they believe this is how they can best serve God and his people. They do not feel called to join a consecrated community or the priesthood. They may be a lay missionary - teacher or doctor - who can more easily respond to need, wherever it is perceived, if they are not tied by an intimate relationship or family responsibilities. But equally they may be a carpenter, office worker, scientist, dentist, train driver, who has a fulfilling personal relationship with Jesus which they feel able to live out more fully if they are not tied by other relationships.
Other people are single because of the situation they find themselves in. This may be a temporary or permanent situation. For example, a young person who is still discerning his or her vocation - whether to marriage or the religious life - is still called to live their life for God while they are single. A person who feels called to marriage but has not yet found their future spouse can be living the single vocation at this time. A person who has been widowed or divorced and thus is no longer living the vocation to marriage may now live out the vocation to single life. A person who is same sex attracted is called to live their life as a single person.
All of these people can have rich, fruitful and fulfilling lives, witnessing to their faith and serving others as followers of Jesus. Many of them would tell you that they are free to do this because they are single, even when it was not their first choice to live alone. A married person must always consider their spouse and children. A priest must consider his parishioners. A consecrated sister or brother must consider their community. But a single person can give all their allegiance to God and his will for their life. Read the testimonies of some single people.