If the only way you define yourself is "CEO" or "founder" you are limiting your identity to your job.
But you also have friends, and family, and a society you live in. You have a body that has needs ("should founders eat good food or bad food?" "should founders exercise in the morning or the evening?").
You are not your job. Your job will go away eventually. Your company might fail.
Read whatever makes you happier, or teaches you more, or entertains you. You don't have to spend your whole life being a "founder".
(I wrote a longer variant of this, coincidentally also talking about what books to read, in the context of "what technologies should I learn?" - https://codewithoutrules.com/2018/02/01/too-much-to-learn/).
