I'm happily resettled and comfortably off now, but I was a single parent for 8 years and desperately poor for 4-5 of those years. I worked, but the combination of childcare and no maintenance meant I was worse off than someone on benefits. I'm not going to lie, it was one of the hardest phases of my life. There were times where I was sat wearing gloves in the house because I couldn't afford to put the heating on once DC were in bed, and many times when I went hungry to ensure my DC had enough food or that I could afford the £7.50 school trip, etc.
Despite all of that, nothing would ever have persuaded me to go back to X. When I left him I rediscovered my sense of worth and self-respect. I also had more time to myself, was able to nurture friendships without feeling I wasn't paying him enough attention and there were a whole host of other little things that make being single enjoyable - sofa to yourself, TV remote to yourself, going to bed when you want to, less washing/cleaning, finding the house as you left it, never being undermined because while all the responsibility may be yours the pay off is that no one is second guessing that decision you made and making you question it. And when you find you can cope, you start seeing yourself differently. Your confidence grows, you try more, you achieve more, and eventually life starts improving.
I went from 'getting by' in a crap relationship, to being desperately poor as a single parent, to retraining into a new career with much better pay and a huge sense of fulfilment because I had done it on my own. And along the way I acquired an extra special bond with my children, deepened friendships in a way I don't think I ever could had I stayed with my X, and even eventually met a new partner through my new job who treats me in a way so different from my X that the contrast is remarkable (partly because these days I demand to be treated well and it has a way of making people react in kind).
Temper your expectations with realism because if you don't the financial difficulties and responsibilities may make you feel like you're 'doing it wrong' when in truth it's normal; but once you adjust you will be fine and definitely happier.
Being in control of a difficult situation with hope for the future and a plan to get there, is infinitely better than a less difficult situation where the future stretches away endlessly towards being unfulfilled and unhappy.
The best tip I'd give you is nurture your friendships. They will tide you through this; and other single parent friends can be one of the most powerful forms of support you'll ever have.
Good luck.