1) Learn to sell.
Everybody sells. Learn how to communicate with people in a way where they not only listen but agree with what you are saying. Learn how to take rejection and build on it. Learn how to ask the right questions that reveal the real reason. Learn how to understand people before you try to solve their problems. Learn how to pitch something in a convincing manner. Learn the art of creating a problem for someone, a good problem, something that makes them reevaluate their current situation and desire to improve it. Learn that you are never just selling one person, there are always more people involved, be mindful of that. Learn what it takes to gain someone's attention and earn their trust. Learn how to care.
2) Learn to write.
Start by writing something bad. A bad email, a bad letter, a bad chapter of a book, a bad blog post, a bad business plan, then keep writing bad stuff until you get called out enough times and you're writing starts to get better. Then read. A lot. Read twice as much as you spend time watching Netflix and twice as much time as you spend on social media. Writing is a form of selling. If you can articulate your ideas into the written word, then your ability to sell skyrockets. It doesn't matter what you are writing, you are still selling something. So, learn how to sell it better by becoming a better writer.
These two skills, in my opinion, are the two most valuable skills anyone in any profession should acquire and continually improve. A close third? How about learning to become comfortable with ambiguity...