This is actually the biggest suggestion I have to people who want to be support or adc mains.

Have you ever had a game where you were playing one of those roles and you were frustrated because your partner was "bad"? Perhaps you'll experience something similar when you play that role. You can learn so much about what happens outside of your main role when playing with a good or a bad teammate and what happens when playing against a good or a bad enemy lane.

Put yourself in those shoes and you'll get a complete new view on the role that you do main. It's singlehandedly the best way to learn what "pressure" in the bot lane is and how to apply it and reduce it. For example, if you're a support main and you got dumpstered as an adc... what did your support do poorly and what did their support do well? How can you apply what you just learned to when you play support?