Surrender to Krishna means to take shelter of Krishna in such a way that it is beyond all common sense, logic and human intelligence. Every day we have to use common sense and logic and intelligence to do even the simplest things of this world. We are trained from birth to behave and make decisions based on acquired intelligence and logic. Having thus been trained from birth; in schools, with parents, friends, our careers etc it is not not possible to go outside our realm of logic and intelligence. But what Krishna is expecting from us through surrender is that we come out of this realm of logic and intelligence, put faith in His words and trust Him in all conditions.
So for example when we are in difficulty the common sense thing to do is to defend ourselves or seek help but a pure devotee who is in full surrender will immediately not think of saving Himself but will immediately take shelter of Krishna seeking His protection. Such an action is devoid of common sense logic. When there is help, we seek it in a reflex way but a devotee will only meditate on the Lord immediately when in danger. Actually a devotee constantly meditates on the Lord’s glories in danger or not.
The reason one should go beyond common sense logic is because Krishna is beyond common sense and common logic. Krishna lifted a 25 mile round mountain when He was 7 years old. Which 7 seven year old can do that? It defies common sense. Krishna is beyond material analysis and thinking. Krishna is beyond our human intelligence. When we have faith that Krishna is indeed Supreme in this way, immediately we will meditate on Krishna beyond common sense and take shelter of Him at all times in that way. The famous example of Prahlad comes to mind where instead of using common sense to protect himself from danger, he simply prayed to Krishna for shelter…rest assured Krishna saved him in all circumstances.
Following in Prahlad’s footsteps, we also have to surrender to Krishna in this way beyond common sense, logic and human intelligence. Henceforth, for this reason people with advanced degrees or for that matter material minded people find it hard to “believe” in a personal God who is guiding everything with Supreme intelligence.