Just like a paper boat floating in water can be destroyed any moment, similarly this human body can be destroyed any moment. However, if we take shelter of Krishna, we can go beyond this ocean of material existence.
Surrender means surrender of your ego.
Surrendering means, "Surrendering the mind to Lord Krishna by thinking only about Him and by serving Him. The natural state of the mind is to think of Krishna".
The tendency in this world is that something has to thoroughly shake us up for us to really take shelter of the Lord.
By surrendering and praying for the causeless mercy of the Lord, the devotee can progress on the path of complete self-realization
Srila Prabhupada’s purport on Sri Isopnishad Mantra 18