You ask three questions. Here are some answers.
1. Life is a marathon, not a sprint. Medium is the same. As is a writing career. Focus on editing your work a little. Make it your goal to be a better writer, not a faster writer. Medium may not be around in five years, but you will be. Learn to write well and it will open doors you never expected.
2. In my career: applying myself to learning new things. On Medium: I joined in June 2018. I decided to do a 6-month experiment in which I would post two blog posts a day and follow two people a day. It was a good experiment and is currently a way of life.
3. There are too many to name. I have enjoyed everyone whom I have engaged with, reading all kinds of things by all kinds of people. I especially love the international nature of the community. The only continent I’ve not yet read anything from is Antarctica.
The very bet to you in 2019.