Ear training builds on itself

Figuring out the first song by ear is the hardest. The second one might be a little easier. The third one is slightly easier still.

And so on.

The more you practice ear training and figuring out songs by ear the better you get at doing it with more complicated songs.

The first one is the hardest and the more patterns you learn and figure out the easier it gets.

The more language you learn, the easier it becomes.

You have more things to reference when hearing a new song. You have more words that you recognize, more patterns that you understand.

And eventually you can figure out how to play a song in a car ride.

ISJ