Mental worship means going deeper, the mantra given by Guru should be chanted incessantly. You have to turn yourself into two individuals. When you rise after your sleep and complete your ablutions, you will have to walk to the tree pick flowers, have a bath, put a Tulsi leaf into your mouth after offering it to god. Physical puja takes half an hour. But mental puja by your other self also has to get up think of God, prostrate to God, and perform all the physical actions mentally including, making up the bed. A very important chore which we should never forget to do. The bed you sleep on should not be left as it is. You should fold the bed sheet at least.
We must mentally walk to a river, or the bathroom for a bath. You must do all this, and spend the exact time you would take physically. Calculate how much time you would need to walk to the Cauvery River and spend that many minutes or hours visualizing it. Physically you might by then getting ready to office, but mentally you will be walking to the Cauvery. Take it from me - if you concentrate on this you will even feel the mud on your feet, and wetness of the water, and enjoy the flavor of the Tulsi leaf in your mouth.
This is what your Swamiji does. I’m revealing the secret to you. You can visualize the actual Saligrama, the Padukas, the idol, and the feet of the Sadguru and yes, even talk to your Sadguru. Actually, you can have a cold water bath mentally and feel the coldness of the water. Believe me! Immerse yourself in this mental austerities and you will really be with Swamiji. The body has to be nourished. There is no way you can mentally drink coffee! Get on with your physical deeds and actions and daily chores but lead a separate spiritually imbued life on the mental level.
Keep this to yourself. This is a secret I am sharing with you. Your Swamiji has been doing this for years now. Physically I am with you but my other self is in constant meditation and prayer. Live your life, one, at the gross level and one at the subtle level. Sat–Chit-Ananda is the real state of the Sadguru and you should experience it. Do not discuss with outsiders, this is my secret revelation to my devotees.
(Q&A Session 22 Nov 2015)