He is in the young adulthood stage of the life course.
Explanation:
In human's life from starting to ending there are some sorts of life stages like infancy, childhood, adolescence, adulthood (young and mature) etc. During infancy baby start babbling, walking with the help of parents where there mind is just in its inception point. Childhood develop imagination power, thinking capacity.
And when one enters into their adolescence stage they become temperamental, quick decision maker. Afterwards, in young adulthood they start to recall their past choices, decisions, accomplishment and be judgmental because that time their mind is fully matured to perceive life's teaching.
