Practice with a rope. Part of learning to lead climb is learning to fall and trust your rope and anchors so you can really push yourself in climbs. Presumably

Practice with a rope. Part of learning to lead climb is learning to fall and trust your rope and anchors so you can really push yourself in climbs. Presumably once you have enough experience and skill at climbing as Alex then you'll start to know what climbs are trivially low risk for you. Alex makes it very clear that when he's free solo climbing he is not pushing his climbing limits or feeling scared--if he has fear then something is wrong and free soloing isn't the right thing in that moment.