How did you know you were ready for a new relationship?

Its been about 8 months since my ex and I broke up. It was a first relationship. The end was messy, it hurt a lot and for two or so months I was truly devastated and struggled a lot.

However, since then I have done everything that you are "supposed to do". No contact, put all our photos in a box and hid it, not checking our chats, her social media and she's muted everywhere. I tried to understand why I had failed in our relationship and so on.

Now I rarely think about her. She's not in my dreams. Her favourite songs don't remind me of her. I visited her city without feeling like the world was ending. Most importantly, I can actually see a future where my life feels happy without her in it. If I picture what she's doing now or who she is with, it feels odd, but it's nothing compared to the feeling of utter despair that I had.

However, there is a new girl who likes me, and quite honestly, I like her. But I don't know if I'm ready. Now and then, a thought about my ex pops up. I can look at our pictures without it hurting, but I do still have a fond feeling for her and that time whenever I look at them. I can't picture my ex and I ever getting back together, but I'm not sure if that's because I know it won't happen, or because I have actually fully moved on.

So my question is, how did you know? How were you completely sure that you had moved on? That you had the ability to love someone new and to love them fully.

Thanks

More than happy to give more context.