YouArentGonnaNeedIt is not the same as forgetting experience, acting stupid, or abandoning morals. It is a challenge to developers to abandon their fears of a far-flung future that may never happen and do an absolutely stellar job of solving today's problems today. Actually, when I violate this rule, it is typically because I am overwhelmed by my fears of not being good enough for today's task. Solving tomorrow's problem is an excellent avoidance strategy, because you can't be proven wrong.
bottom line: just focus on the very "now" you got