Cheerfulness and the Gospel of Christ
Naturalness, sincerity, and cheerfulness are indispensable conditions for the apostle to attract people.
If you're not naturally a cheerful person (you may have a temperament that inclines you to brooding and solemn reclusion, for instance), don't fret. St. Escrivá explains the source of the apostle's cheerfulness—and it isn't ultimately your temperament.
He explains in #185:
When you launch out into the apostolate, be convinced that it is always a question of making people happy, very happy: Truth is inseparable from true joy.
Christ's Gospel is good news. The euangelion—the Greek word that gives us evangelize—is quite literally good news. Its truth should, when all is said and when all is done, cheer.
Sticking to the truths of the Catholic faith, even if that adherence bring us into opposition with others, isn't a depressing or melancholy business. Though the world may not like to hear it, what the Church has to say is meant to make it a brighter, more cheerful place.