It is a practical experience, that in every field of life, if one wants to learn something one needs guidance and help of a more experienced and advanced person. If it weren't so, one wouldn't have opened so many schools, institutions and educational institutes, which offer one the possibility of accepting the role of a student and thus learning and making progress in a particular field of knowledge. But the learning process is found not only in an organized way as mentioned above, but it is a kind of spontaneous and natural exchange of 2 individuals, namely one in a role of teacher and another in the role of a student, which can be easily experienced on a day-to-day basis everywhere. Just remember for example Your father teaching You how to drive a bicycle or Your friend how to drive on skateboard. You weren't even concious about it, yet You naturally and with joy accepted a teacher, and happily listened his instructions, thinking them to be for Your own benefit.
Spiritual education isn't any exception in this regard. A living entity, after its long journey in this material world, suddenly feels the need of knowing the higher truths of one's own existence and the universal principle behind it. Understanding one's inability of knowing these things alone, he start looking for a suitable teacher. On his path, he finds different teachers, who gradually help and teach him according to his qualifications and specific desires of how to approach the Absolute Truth.
For one, who wants to know and near the Original Personal Aspect of the Absolute Truth, Lord Gauranga-Krishna, the same Supreme Personality of Godhead manifests in the body of a spiritual master, who is completely ready to guide the soul back to His Kingdom. The same Supreme Lord takes a form of different persons, in order to take charge of so many different aspirants, at so many different stages of their evolution and under so many different circumstences. But ultimately it is the Supreme Lord Himself, who is the actual and only quide. Therefore it is natural and absolutely not controversial if one feels inspiration and accepts guidance from more than one spiritual teacher, understanding it to be a wise, perfect and munificient arrangement of His beloved Lord. Nevertheless, out of them, one bears the authority of higher importance, in order to clarify and set the direction in case of apparent disagreements and controversies.