It happens at times. Sometimes when you're lucid you just don't think of your lucid goals, but if you ask me, that's actually a good thing. If the only ideas we got to do stuff in our lucid dreams came from our waking lives, then what about being whipped into lucid dream situations we don't predict or construct prior? It's cool to have control of things you usually don't have control over, but it's not cool to always take control every single time. Sometimes, you just gotta let the subconscious do some of it, then take advantage of the situations presented to you - in other words, don't JUST do goals. Do different things as you come up with them in lucids!