When I was learning the Mozart Clarinet Concerto for a performance years ago, I practiced as I jogged. I heard and felt the piece in my body phrase by phrase, back-wards from the end to the beginning. This practice also helped me memorize it. While my body flowed and loosened during jogging, the beautiful music played through me. Without the instrument, I was able to idealize how I wanted it to sound when I played.
If you don't have the sound and the music in your ear, your body won't know how to get there, what to do. No teacher can teach a student who doesn't hear what they want to sound like, who they want to sound like. No teacher can teach a student to love a phrase of music beautifully played by a great musician.
If you want to become a musician, listen to recordings. Fall in love with them, live them, breathe them. Go to concerts and find what you love about the music and the performance. Yearn for the satisfaction of hearing music played beautifully. Let your ear sing and play with the music as you hear it. Feel it in your body as you enjoy it.
Listen carefully. Listen critically. Watch closely, if it's live. By critically I don't mean finding mistakes. I mean hearing detail. How does rhythm emphasize the shape of a phrase? How is pitch used? How is vibrato used? How does the body express the music? How is tone used?
Imagine these things with your body. Imagine being that musician as they play. Become them in your mind.
When practicing, let go of your judgments. Keep the ideal in your ear. Let your body flow toward that ideal. Relax into that flow.
Now you are ready for a lesson. Now a teacher can help you learn.
Even for professionals, hearing before playing is essential.