1、It is never too old to learn.

活到老，学到老。

2、There is no royal road to learning.

学问无坦途。/书山有路勤为径,学海无涯苦作舟。

3、A man becomes learned by asking questions.

不耻下问才能有学问。

4、Absence makes the heart grow fonder.

小别胜新婚; 距离产生美; 久别情更深。