I (M25) just got dumped in my first relationship, how do you avoid getting attached early on

Tldr: Got attached in a one-sided relationship, was it a mistake to get attached too soon

For context, I was seeing a girl for the last ~2 months and felt like things were great between us. I ended up getting attached before making things official and accepted excuses for red flags around the relationship because of it. It felt out of nowhere when she was a bit closed off on a date and then broke things off two days later.

I'm having a rough time given the 100 to 0 of it all. Is it normal for relationships to be one sided when they don't feel like in the moment? Did I make a mistake letting myself get attached so early?

I feel like this being my first experince with relationships really doesn't help with things lol