24 Yet man must respond to God Who calls, and that in such a way, that without taking counsel with flesh and blood (Gal. 1:16), he devotes himself wholly to the work of the Gospel. This response, however can only be given when the Holy Spirit gives His inspiration and His power. For he who is sent enters upon the life and mission of Him Who "emptied Himself, taking the nature of a slave" (Phil. 2:7). Therefore, he must be ready to stay at his vocation for an entire lifetime, and to renounce himself and all those whom he thus far considered as his own, and instead to "make himself all things to all men" (1 Cor. 9:22). Announcing the Gospel to all nations, he confidently makes known the mystery of Christ, whose ambassador he is, so that in him he dares to speak as he ought (cf. Eph. 6:19; Acts 4:31), not being ashamed of the scandal of the Cross. Following in his Master's footsteps, meek and humble of heart, he proves that His yoke is easy and His burden light (Matt. 11:29ff.) By a truly evangelical life, in much patience, in long - suffering, in kindness, in unaffected love (cf. 2 Cor. 6:4ff.), he bears witness to his Lord, if need be to the shedding of his blood. He will ask of God the power and strength, that he may know that there is an overflowing of joy amid much testing of tribulation and deep poverty (2 Cor. 8:2). Let him be convinced that obedience is the hallmark of the servant of Christ, who redeemed the human race by His obedience. The heralds of the Gospel lest they neglect the grace which is in them, should be renewed day by day in the spirit of their mind (cf. 1 Tim. 4:14; Eph. 4:23; 2 Cor. 4:16). Their Ordinaries and superiors should gather the missionaries together from time to time, that they be strengthened in the hope of their calling and may be renewed in the apostolic ministry, even in houses expressly set up for this purpose.
Source: Ad Gentes (Vatican.va)