求翻译：但随着年龄的增长，必须建立起内在激励系统，如果学生不能从心理内部来激励自己，他们永远也不会体会到学习的乐趣。是什么意思？

But with the growth of age, you must establish internal incentive systems, if the student is not from within the psychology to motivate, they never feel joy of learning.