When you were in elementary school learning to read and multiply, those things seemed hard. Now you do those things everyday without even really thinking about it. The more you read the better you got at it and now you read these words with ease.
How did that come about? PRACTICE.
Whether you work at Dunkin Donuts or are a rocket scientist - both need practice and perseverance to do the job well. Learning to deal with difficult people who are hungry for a donut does not always come naturally and neither does getting the thrust correct for your rocket launch.
Trial and error is what we call it, but it really is practicing.