*Then today, when something that is objectively positive has happened, I can't stop crying. I don't understand my own emotions.
I've been so focussed on H and DCs and their happiness for so long that I have no idea what brings me joy*
Totally understandable emotional reaction.
You have been holding it all together for your precious DC and now a part of your brain has spotted that it's not all on you, so the part holding it all in can ease off a bit, set the burden down for a moment.
And it all floods out, familiar and unfamiliar feelings that you have just had to put on hold while sorting everything else out, putting yourself last.
Now, you can pay attention to your needs and wants snd, yes, it's terrifying.
This is the start of a new chapter for you. In good time, you can start to pick up the pieces and look for the joy in your life.
For today, though, I'd be tempted to explore things you would usually never consider. Naughty things.
Spend the afternoon verging out in the sofa watching old reruns of slushy movies. Or rereading favourite old books. Pretty much everything will be on YouTube or something.
For me, the entire Anne of Green Gables series (l m Montgomery). Predictable, safe, nothing totally bad happens so you can really let go) is the perfect excuse to sob my heart out while gorging on sickly chocolates. Fish and chips. Anything you usually deny yourself, offer your self a taste just to establish whether it really is what you fancy right now.
Or dress up and go and have a cocktail in a smart London hotel.
Or whatever you fancy right now.
No need to take any consideration further than a few hours ahead.
Take it easy on yourself. Things really will get better from here onwards. All the best.