Only child and done

I need some advice. I have 1 child and she’s 8 years old. I’m only 28 so I’m still young but also have not been in a real relationship for a long time. Her dad passed when she was 1 so she’s all I have and I’m all she has really. I also feel a little traumatized as being the only parent has been so hard for me. I’ve always said I would never bring men in and out of her life and I’ve stuck to that. I want her to know who her daddy is and keep his memory alive… but I feel so guilty. I feel like I’m setting her up for failure. I try so hard and never feel like it’s enough. Or I feel I’m always doing the wrong thing. She has cousins she plays with, neighbor kids, and even play dates sometimes with kids from school… but there is also a lot of alone time with just me and her. I try to do fun things with her but that can’t be constant. She’s never been interested in sports. When I ask if she would like to try a sport she tells me no way.. and honestly I don’t know if I could afford to keep her in sports if she wanted to. I just feel guilty and truly don’t want anymore kids. Even if I did, I’m not in a relationship. Have any other mom’s been in this situation or are in it now.. any advice?