I venture to suggest that the pronoun “en” here is related to an omitted noun.
There is a phrase apprendre les choses de la vie where you can notice a noun “choses”. In your sentence, however, it is omitted. When you omit a noun in such a way, you should use “en”. For example:

• J’achète des pommes = j’en achète.
• J’ai deux enfants = j’en ai deux.

Hope it helped.