how do i know if i (m18) know if i still like the (f19)?

I (M18) broke up with my girlfriend (f19) a few weeks ago but now I miss them and I dont know if it's because of some sort of grief period or because I made the wrong decision. I had and on and off mindset about it for a while and I couldn't get the feeling that something was wrong I'd been with them since I was 15 and near the end it just felt like I was losing feeling and I wasn't always happy, even though she did nothing wrong. either way I finally made the decision to end it when I realized I wasn't 100% devoted and I felt terrible dragging her through it if I didnt want to invest. she was super hurt and I feel terrible to the point where I think it would be too toxic to try go back but I keep feeling this feeling of missing her and knowing that it's all my fault and that I messed up a potentially amazing thing. how do I know if I made the right decision?