Your feelings are 💯 valid. It's a brutal end to a dream; heartbreak and bewilderment and no doubt financial difficulties thrown in too.
I know when my marriage ended I was at first in shock and then panic about how I would cope.
It would be easy for me to say, hey you're in good company, you'll get through this, but that's too glib. You need time to process what has happened and yo get used to being separated/lone parent. It's a big adjustment.
Can you try to take it a week at a time? Set your goals fairly low ie get the kids out the door calmly each morning, have a plan around meal times, and ensure you're getting at least 30mins a day of being alone. That is, undisturbed, no chores, just quiet time.
It's important to focus on your wellbeing ie. keep a regular bedtime and wake time, eat regularly and mindfully, and prioritise time with people who care about you whether that's a family member or a friend.
Keeping things simple and routine will help you to stay calm, and after some weeks/months, you'll realise that you're managing very well. Your confidence will grow and you'll be able to reflect on your new found strength.
That's the point at which you'll realise your life is infinitely better than you could have hoped, and how much strength you have. You'll start gaining ambition, pushing yourself to try new things and stand up for yourself more.
I'm sorry for the pain you're experiencing right now. Let yourself feel whatever it is that rises up inside you because it'll pass more quickly that way. But I promise you that the pain will reduce and your confidence will grow.