Children can't do whatever they want; they need rules.
Tips
history
This idiom comes from the Analects of Confucius (《论语》). At age 70, Confucius said: 七十而从心所欲不逾矩 - 'At seventy I could follow my heart's desire without overstepping the rules.'
usage
随心所欲 can be positive (freedom) or negative (reckless self-indulgence), depending on context. It's often followed by 地 when used as an adverb.
