Op I am sorry that he has left and you have every right to mourn the future you thought your child would have. I am a lone parent (although it happened after my child was born) but I wanted to lost some of the positives so that hopefully at some point you can turn this round in your head as I have done.
No disney parenting, what I say goes and discipline etc is very consistent.
I can book whatever, whenever, I don't have to worry about what dates my ex wants our child or if he will call and cancel a visit.
Doing it alone is far better than doing it alone but with a useless partner in the house doing nothing and the house stays clean etc.
Family who do help are enthusiastic with their help.
Families are made up of all sorts nowadays. My son has friends with 2 dad's or 2 mums or who are Foster kids. He understands its us but we also say friends are family and we have close family too. There is no such thing as a perfect family.
Your child will have an amazing role model, a strong working mother who loves them.
It's genuinely fun spending time with your child and people accept you come as a 2. Real friends adapt. They come here for dinner after he is in bed or we meet at lunch time etc.
Being single is pretty great, the bed to myself, the remote is mine, I can leave the washing up if I don't want to do it, I redecorate how I like, no one criticises my body, I can go to bed when I want and am in control of all the admin so I don't get stressed because someone isn't pulling their weight.
Of course there are times it is tough but on the whole I want to say I love being a mum, I love being single and its not half as bad as its made out to be.