My suggestion would be:
Bleibt begierig, bleibt offen.
begierig differs a bit from the other suggested translations, but I think it is simply wrong to translate it as
hungrig. It is true that terms like
abenteuerhungrig do exists, in which
hungrig is used to express desire, however the short form suggested here does sound more than strange to me. Ultimately, he refers to insisting on a burning desire, an apetite for challenge, one such that claims you and takes hold of you, and thus I ended up with
gierig, and in this case, the slightly milder
begierig. Equally to
begierig has the objective negative meaning of strong want for something, yet
begierig does also have a certain amiable and well meaning tone to it. (Er trank seinen Becher begierig aus. - meaning not he was greedily drinking, but he enjoyed it.)
bleibt offen translates the meaning more than the implication of the word. Obviously
bleibt offen does not reflect the notions of true foolishness, that his saying does not explicitly exclude it. However, it is my point of view that at the core, the foolishness he refers to, is a constructive and creative one, not a genuine one.