As of my last update in September 2021, I don’t have any records of an exact quote matching the one you described: “Woe to thee that contemplates what came before and what comes after.” It’s possible that the quote might be from a less well-known or obscure source, or it could be a paraphrased version of a more commonly known saying.
The concept you mentioned, however, aligns with certain teachings in various religious and philosophical traditions. In Judaism, there is a focus on living a righteous and meaningful life in this world while also holding beliefs about the afterlife (Olam Haba). The idea is not to get overly preoccupied with the mysteries of the afterlife but to concentrate on fulfilling one’s purpose in the present world.
It’s also possible that the saying is a more modern interpretation or creative expression of such concepts. The best course of action might be to consult with religious scholars, spiritual leaders, or experts in Jewish literature to see if they recognize the quote or can point you to similar teachings within Jewish texts and commentaries.