What do I do with my reactions? Listener question

I’m not sure if this is about boundaries or just reactions sorry, or maybe that’s the same actually.

I was listening to your podcast episode on boundaries and expectations in relationship.

I’ve actually been questioning my reactions over the past week, and this is just fascinating. At my age I’m amazed that I’ve not learned to look at myself in relationship this way EVER before so this episode is groundbreaking for me!

What is the solution when we recognise one of these behaviours playing out that is not about the other person. Like my anxiousness when my new partner doesn’t text me back for 5 hours, or acts in a way that “makes” me feel anxious?

Instead of responding in a defensive or needy way, I am trying to notice it and not act. But now I hear this, I feel like this is as you say as the other extreme, allowing “someone walk all over me” which is not happening but I’m still allowing something that doesn’t feel ok with me at the moment. 

What do I do with these reactions of mine once I notice them? How do I actually go about healing them?