If we accept Sikshastak as authority given by Lord Caitanya, this means we accept Lord Caitanya as Spiritual Master. In the Bhagavad-gita it is openly mentioned that Arjuna accepted Krishna as the Spiritual Master. There is another mention in the Sikshastak, Lord Caitanya says "I do not want any wealth of this world, I do not want any following, neither do I want a beautiful wife. Simply I want to become a servant of the Lord.'' To become the servant of the Lord means to accept a Spiritual Master. Without accepting somebody as master, how can one become an expert servant? It is not that in every literature you will find the words that everyone has to accept a Spiritual Master, but we have to study things scrutinizingly. In the Caitanya Caritamrta there is mention guru krsna krpaya paya bhakti lata bija [Cc. Madhya 19.151]. By the mercy of the Spiritual Master and Krishna one can get the seeds of bhakti lata, the plant of devotional service.
Letter to Jaya Govinda, 4 July, 1969