Something else that comes to mind, which may be relevant to this topic:

Try not to allow yourself to be pressured or pushed on the spot. It's perfectly okay to take a moment to think about the most appropriate response for your needs in the situation. Even a very brief, contemplative silence can be unnerving for a bully who's trying to control the situation and get something they want from you. Stopping and thinking before responding can often put you back into feeling in control of the situation, and yourself.

In some situations, it's also okay to buy time- i.e. "Let me think about that and get back to you tomorrow."

You already know these things get easier with practice. You're doing well, and will keep building that skill set the more you do it.

It's definitely okay to think up scenarios that could come up, and then appropriate responses you could use. That's still practice.