This isn't my partner but my 'best' friend who is male.
There's a bit of history in that a couple of years ago he got a girlfriend and obviously she tied up a lot of his time, along with his kids and job etc. Which was all fine but then last June he 'dropped' me and completely cut contact. I found it all very hurtful but I got over it (sort of). I was working, pregnant (to my husband!) so really busy anyway and I moved on. His timing was well off as I don't have many close friends and I would've liked him to have been in my life. He had recently been letting me down a lot and sapping my energy so I tried to see it as a good thing. I posted on here at the time and got some great advice which I followed.
In November when my baby was 8wo I randomly got a massive long text from him saying how sorry he was about dropping me and all the let-downs, how much he needed me in his life, basically begging me to 'salvage the friendship' as he felt I'd left a void. I was really 
but after a few texts back and forth we decided to meet up. We met up quite a bit and it was like old times. He split up with his gf (nothing to do with me!) and got a new job, and I went back to work myself. Then throughout June he would arrange something with me and then cancel at the last minute (which was annoying as obviously with working FT and having my daughter now arranging anything is a military mission). He would always blame his new job which I suppose is fair enough because I know where he works is manic, but he would often leave me hanging without even a text to let me know what was going on. We work at the same company on the same site so it's not that hard to just go have a coffee yet I haven't seen him since May because he keeps cancelling.
He seems to be doing exactly the same as he did last year. My birthday came and went with no word from him. I'm not bothered about a big fuss but it seems symbolic that he forgot it, iykwim. I know he's wrapped up in himself and his job at the moment (he's actually at a festival so it's not work) but if I meant that much to him wouldn't I at least get a Happy Birthday text? I don't get it. Why the big appeal to salvage the friendship if he was just going to put me through it all again? Is he some kind of sadist? I feel like a fool for making up with him for him to put me through this again. Because now I have to go through the whole process of feeling like an idiot, missing him, etc etc and I can't believe I was so stupid.
And I genuinely don't believe he actually realises he's done anything wrong, maybe he hasn't. I don't know.