Wallow for a while but only for an hour at a time! Acceptance of the situation will help. Accept it didn't work, won't work so don't try and take them back/talk it over/sort it out. That's already been done.
Go forward one day at a time, every day is a gain, every day is progress towards building a new life for yourself. Do not contact the ex...you will just take steps backward, get upset again, have to start again.
Sleep well, eat well, don't overindulge in anything, pamper yourself...candles, long baths, new bedding, play music, dance, have the odd lie in, or watch a film in the afternoon to distract yourself. Buy a colouring book or puzzle book or jigsaw or a magazine you don't usually buy.
But also take long walks...there's nothing like it especially when the weather is good. People you meet on walks are often friendly, a smile can often cheer you up. Go somewhere you haven't been before, preferably somewhere away from traffic where there are trees and grass and water. Green surroundings are good for the soul.
Then plan. Plan your days...cinema, window shopping, go for a swim, a massage, a walk, go to the library, a drive or bus ride, look up groups you can join in the daytime or evenings, volunteer in some way [charity shop/hospice/kennels]...try and keep busy even if it's something small like clearing out your wardrobe or kitchen cupboards. You are making a fresh start...out with the old.
Then long term plans...a day out to a new town or village, a weekend away, buy a bicycle!, plan a holiday, a trip to the theatre, can you grow some veg/flowers in the summer? perhaps get a small pet?...anything nice in the future to look forward to.
Keep your life full of activity somehow but also times to relax. I'm getting over the loss of someone now...I've been going to the cinema a lot, some good films about, and I've found an new interest in English history after 'The Favourite' and 'Mary Queen of Scots'. I am off to bake some rock cakes now and catch a favourite tv show later. I have a book from the library I cant wait to start too...
You'll be fine, good luck.