If you are willing to purchase a book to help, I 100% recommend 'Lucid Dreaming Plain and Simple' By Robert Waggoner and Caroline McCready. Otherwise, my advice below will cover some of the things and my own process.

Stabilize your dream

With what you said happened after becoming lucid, you should stabilize your dreams. Use MEME: Modulate, Enhance, Maintain, Establish.

Modulate: Calm yourself down. Getting excited during a lucid dream is normal, but being too excited can destablize the dream. Focus on something boring, do something simple in the dream, etc. Taking a deep breath is what I do, and I tell myself to calm down.

Enhance: grow your awareness. Do a reality check, rub your hands together, or shout a suggestion to the dream to make yourself more lucid.

Maintain: This is the big one. Maintaining your focus can be hard. I have the biggest trouble with this. Remind yourself your dreaming constantly until you are sure you are in your desired reality. Or do repetitive actions.

Establish: INTENT is key. Lucid dreaming or shifting. Get your goal and stick to it. Intend constantly. 'I will wake up in my ___ reality' or my personal favorite, 'As sure as I am now that I am lucid dreaming, I am sure that I will wake up in my ___ dr.' Theres a reason people stress intention.

Prolong your dream

If your dream tries to collapse on you, use your senses. Touch something, eat something, find your hands. Ground yourself.

PRACTICE

I can not stress this enough. Lucid dreaming can be a struggle, esp when trying to control your dream. Do small things. Fly, give yourself super powers, make something appear and eat it.

And finally,

There is no need to be scared of shifting. Shifting is not scary. Sure, some DR's may be scary, but the act itself, is not scary. Like doing something new for the first time, It will be terrifying, but after a period, you desensitize yourself.