Still grieving a discard from last month

I am almost 40, grew up with family members with Cluster B traits, and (surprise!) I have zero history of long term relationships. My most recent relationship attempt lasted a grand ol 6 weeks. Started off intense, he idealized me, and as I was already lonely, I fell for everything.
He admitted in the beginning he had mental health problems, including self-harm, constant mood swings, emptiness, pushing people away, self hatred, and others. In hindsight, yes, there were definitely red flags.
Everything was going well IMO then he discarded me like yesterday's garbage overnight! (Nothing catastrophic happened because he was still showing up online etc). I tried to reach out several times within those first 5 days as politely as I could be. Nothing. I did nothing wrong, but I still hurt. Part of it is my yearning for LTR, so I admit to doing some idealizing myself. This man has never been diagnosed BPD, but I can't think of any other clinical reason for his BS behavior?!
Regardless, I cannot change the past, and I can only work on healing myself. Now in therapy once a week because after growing up with Cluster B family, it is no coincidence nearly every person I have tried to date has a BPD diagnosis on paper, or very similar traits. My therapist even pointed out I did not truly miss those red flags or BPD suspicion, but I found it more tolerable than staying alone. Yeh sounds right.
To others on here dealing with this, what were some ways which helped you feel better? Therapy? Support groups? I'm not crying as much as I used to, but it still stings so much!

Hey PL,

Yea, unfortunately it does just take some time too. At least you are fully aware of repeating the pattern of getting involved with cluster B personalities, but as you know too, they don't change until/if they chose to do so, and even then, it can take them a lifetime to improve.

As you also know intellectually, there is a big difference between being driven by 'I don't want to feel alone', and being driven by 'I want to feel good about myself, my relationship, my life'. For those who learned the former, it's hard to make that change without some epiphany moments.