By conquering your own fears.
This can be done by several means.
Simplest and most powerful of all is a complete faith and trust in the Divine Grace. If it is lacking then one can additionally offer one’s fears to the Divine with a prayer for protection.
You can also reason yourself out of the fear by analysing it.
What is important is to not let your fears prevent him from undertaking challenges and activities that are reasonably safe.
Finally equip him to handle the challenges by making him grow conscious of himself and his environment so as to become aware of any lurking danger and ways of dealing with it. For this it is good to inculcate in the child habits and attitudes such as prudence, vigilance, courage, ability to stay calm under challenging circumstances through exposure to proper physical education and sports.
Affectionately,
Alok da.