See, my 1-3 days wasn't wrong!

Now that this has happened a couple of times and your period has then started each time, perhaps next month you could set yourself a challenge to try and not panic about it until x amount of time has passed. For example, 3 days. It's hard to not stay fixated on it once you've already started panicking, so maybe the key is to prepare yourself beforehand and say "hey, I'm going to get some pink/brown for 1-2 days before it properly starts. This has happened already more than once, it's normal for me".

You can't control your period but you can control how you feel about it.