The more one immerses oneself in the thoughts of Sri Guru, the more the attachment for Nitai deepens. And the more one thinks about Nitai, the more one feels separation and love for one’s Guru padapadma.
When we are with our spiritual master, we are automatically forced to remember Nitai, since our Gurudev is constantly meditating upon Him. So being with Guru = being with Nitai. And when we are associating with Nitai (via the processes of devotional service and His holy name), we cannot help but remember our spiritual master, since He is the one who has gifted us with that association of His Lord and Master. So being with Nitai also equals to being with Gurudev. This shows that the two are eternally inseparable.