Hey Juju - I totally empathize with how you're feeling.
Just like Dawn said, counseling helped tremendously in the beginning just to get me straight and out of feeling continuously blurry. I haven't been to counseling for the last five months because I got out of it everything I needed to. However, it helped me get good grounding for sure. I have a research background and so I sought out everything - from clinical studies to personal growth books. I focused a lot on emotional health and how to stabilize life by working through past traumas and also BD. I learned a lot about myself, my behaviour patterns, and where they were stemming from. Once I got to the root causes of my behaviour - abandonment and rejection - I was able to really work through a lot of my built in instincts and move from living in survival model to just breathe and live life with a sense of calmness. Also helped me to re-story my life and truly figure out how much strength and resilience I have after all that I've been through for the past few decades. I was able to understand and name my depression and its roots.
The other major point, which is so counter-intuitive, is that I haven't dated yet. Just as Dawn mentioned, I needed to take the time to focus on myself and get my life on track before I opened myself to the world. I did get a dating app to survey the landscape and I wasn't too impressed. I also didn't get any hits on my profiles, which was super annoying. I realized that the dating apps weren't for me right now because it was fueling my rejection traumas and that wasn't healthy for me. I have gotten quite a bit of interest in-person from women. This is partly because I come across a lot differently than an online profile. I also don't know if me mentioning I had kids was a turn-off for women on the online apps. Anyways, I am not dating right now but I tentatively plan to dip my foot back in sometime in the fall of this year. I still need time to get some things right in my life and I want to dedicate time to that.
I feel you on the rejection from the angle of a spouse. My exW is already dating someone and it really stung in the beginning when she told me. I had to take a week for my emotions to settle and reflect on this new turn of events. It was like getting rejected all over again - but now with a name and a face. The only way I have been able to fortify myself is working on my self-value and worth. There is no way to directly attack the sense and feeling of rejection. My path has been to do things that bring me joy, happiness, and a sense of personal value to mitigate rejection. Cultivating emotional fitness and trust that you have value and self-worth is the path. I crush it at my work, my health, my parenting etc and those give me data points to tell myself that I am worthy and that I have value. So, when I see rejection in my face, I know that it is just exW's preference, not an indictment to who I am. I also remind myself that I don't want her back which helps.
So it's a lot of things done daily and over time that builds that self-value. I know that it doesn't make me immune to feelings of sadness, hurt, anger. But I know how to navigate them better now.
I wish there was a simple answer to it, but life is way more rich and complex. All I know is that I have the ability to change my narrative and the perspective that I can take on any given thing. I always listen to what my initial feeling and response says, but I choose to take a wider perspective.
As Viktor Frankl says - "Between stimulus and response there is a space. In that space is our power to choose our response. In our response lies our growth and our freedom." I wholeheartedly not only believe that, but I have seen it through personal experience the power behind it.