Quick to explain, but oh so true…
Take our your iPod, or your favorite MP3 player. Pick a track at random and play the first 30 seconds.
Now sing the tune. Easy isn't it?
Now pick up your instrument and play the same tune.
Can you do it first try?
Yes? Then you have mastered your instrument.
No? Clearly you haven't mastered your instrument yet. But if you can sing the tune, you will be able to play the tune by ear, just as easily as you can sing it. You just have to know your instrument as well as you know your voice.
Your voice is with you all the time. It has been all your life. So you can sing any tune, any time. When you know your instrument as well as you know your own voice, you really can say that you play pretty well!
Step 1: Take your instrument with you everywhere you go. Yes, even the toilet. (Which could be the ideal place to practice in peace!)