Go to sleep as normal to become lucid. That's what works for you!

Your lucid dreams are becoming nightmares because you're fearful. You're only going to have a nightmare if you're scared in your dreams. Find and eliminate the source of fear and the monster will probably go away.

For example, instead of thinking the zombies are chasing you because they want to kill you, try thinking that they are because want to hug you. You're in charge of what they want.

Optimism generally leads to good dream control and pessimism leads to the opposite.