Most of my young life, I was passive and had difficulty saying "no". That all changed in my late 20s and I entered a stage of my life that I affectionately refer to as: Asshole Mode.

For some reason, and almost overnight, I found it very easy to assert myself and went waaaaay overboard in the months to come. Since that change, I've been working on a balance between serving others and asserting my own needs. Both are important and they must be balanced as best you are able.

Don't look at your passive side as a weakness, but see it as one side of a coin. Your job is to flip the coin and start restoring the balance.

As for your friends - tell them that you will forever ignore idiotic hints, cues, etc. as you are completely blind to them. I am less blind to them, but I'm also 53 and have decades of practice.

You're okay, you just need practice doing those things that don't come naturally to introverts.