Lord Nityananda, who is Balarama Himself, the first direct manifestation or expansion of Krsna, is the original spiritual master. He helps Lord Krsna in His pastimes, and He is a servant of the Lord. Lord Caitanya is the same Lord Krsna, and Lord Nityananda is Lord Balarama. Lord Nityananda fulfills all of Lord Caitanya’s desires. The source of the sentiment of servitude is indeed Lord Balarama, and the plenary expansions who follow Him are all influenced by that ecstasy.