One must execute devotional service under the guidance of a devotee or directly under the guidance of the Supreme Personality of Godhead. It is not possible, however, to train oneself without guidance from the spiritual master.
In spiritual life, one must conduct one's whole life under the guidance of the guru. Only one who executes his spiritual life under the direction of the spiritual master can achieve the mercy of Krishna.
Bhaktisiddhanta Sarasvati Thakura advocated that every devotee, under the guidance of an expert spiritual master, preach the bhakti cult, Krishna consciousness, all over the world.
A devotee should not be proud of his acquisitions. The symptoms of a devotee are meekness and humility. Although spiritually very advanced, he will always remain meek and humble, as Krishna Das Kaviraja Gosvami and all the other Vaisnavas have taught us by personal example. Caitanya Mahaprabhu taught that one should be humbler than the grass on the street and more tolerant than the tree. One should not be proud or falsely puffed up. In this way one will surely advance in spiritual life.