I generally think of boundaries on as they relate to myself/my own. If I keep healthy boundaries, my life is so much less stressful.

I had healthy boundaries described this way once. A healthy boundary is not a wall, it's a high fence with a gate that I control as needed. I can see through the fence, over the fence, etc. I can put spikes on the top of the fence or electrify it if I want to. I can lock that gate if need be. But I can open up that gate for freer movement as needed and still have the ability to close the gate if the open movement becomes a problem.

Everyone around me also has their own fence and gate (ideally) that they can work the same way. I have to realize they have the right to decide how to work their gate where I am concerned and I must respect that right as I would want them to respect my choices about how to work my own gate.

No one has the right to try to get into my fence without my permission, to try to climb over or dig under no matter how much they want to. I cannot do that to others either no matter how much I want into their fence.

Seems simplistic, but it was a good, concrete visual for me that made sense.