Answer:
Greg has seemed to matured into understanding that crawling over an edge may lead to falling
Explanation:
Based on the scenario being described within the question it can be said that the Greg has seemed to matured into understanding that crawling over an edge may lead to falling. This fear of falling and potentially getting hurt is preventing him from crawling across even though he is being encouraged by someone he trusts (his mom). Fear is a strong motivator or prevention mechanism in this case.