When it comes to boundaries, enforcing them can be the hardest part. It's easy to feel nervous and possibly even guilty for sticking to your boundaries. Practice before jumping into saying "no" to others, especially to toxic people you may have in your life.
Setting healthy boundaries in your every day life is an important first step in taking care of yourself and your mental health. To help yourself start out, use a worksheet. You can find some online, or you can make your own. This will help you work through enforcing your new boundaries. List your boundary and create a consequence for crossing it. This is where practicing with yourself first will come in handy. Perhaps you are in contact with someone who has a tendency to raise their voice with you, causing your anxiety to rise. If they begin to raise their voice, you can tell them that you will not continue the conversation unless they lower their voice. If they refuse, you have to be able to let yourself walk away.
The journey to making healthy boundaries takes dedication and hard work on your part, but it's worth it. You're worth it. You deserve boundaries to give yourself a better life. You have the tools and you can do this. May the odds be ever in your favor!