Have a positive attitude about your ability to learn

You have to believe you can do it. Without this belief all is lost.

Then...

Good attitudes are maintained through focused effort and disciplined study in alignment with your goals and values.

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Update September 2020
Good attitude is easier to maintain if you are sharing this journey with other people. You can meet other adult piano students at professional piano recitals. Strike up a conversation with the person sitting beside you. Chances are good that only pianists and former pianists attend piano recitals.
David