Have discipline
For me the main thing is discipline, if you don't have discipline there is no Pro player and the Pro players themselves tell you that.
Control of emotions
In poker, emotions have too much variance. The famous downswing must be learned to see it as a learning experience rather than as a time of bad streak. Analyze why it happens. Is it a bad streak??? or is there part of my game that I should improve???
The famous "tilts" are even life issues. How many times do we put ourselves on "tilt" in life itself???
It is not only celebrating the good streaks, but incorporating everything into the game so that the profit line is positive in the long term.
Absolutely respect your bankroll
This question is in reference to the fact that although every poker player has to draw from his bankroll for his daily life economically, he must respect this bankroll in the sense of playing at the levels in which you can access according to your bankroll.
That is, do not play cash tables or Mtt's in which the entry does not destroy your bankroll (Example, if your bankroll is US$100, play US$1 tournaments and do not play US$10 tournaments)
Study
This is essential. Have some study time daily, in the way you like best. Watching videos, reading, checking your
hands with a program, doing a course, etc.
Practice and play daily
This is also essential. The recommendation could be to play at low limits and put study techniques into practice.
It is also very important to respect rest times.
Cheers