Playing by ear is a journey, not a destination. Keep practicing, keep listening, and keep pushing yourself to play without sheet music. It's a skill that will serve you well in your musical endeavors.

I suggest exploring modal harmony as well. Modes like Dorian, Mixolydian, and Lydian can add unique colors to your chord progressions and help you break out of the typical I-IV-V patterns.

I've always admired the Beatles for their innovative approach to songwriting and it's interesting to hear how their music can be used as a learning tool for music theory. I'll definitely have to give playing along with their songs a try and see what new things I can learn.

Don't be afraid to step out of your comfort zone and try new things. Sometimes, the best music comes from pushing yourself to explore different sounds and techniques.

I've noticed that many adult beginners tend to struggle not because of technical issues, but because of their own expectations. They often expect quick progress and get frustrated when that doesn't happen. Do you agree with this observation?