Apps & notifications
Google LOVES notifications and Android is filled with them, which can be good but also stressful for a lot of people. This is why this tip is more of a reminder that you should manage them.
The easiest way to manage notifications that you find annoying or unnecessary is to long press them in the notifications overview. This will give you the option to turn them into a "silent" notification, meaning that it will still be visible from the notification overview but without a sound and vibration. If you want a more detailed overview with all notifications settings, simply press the cog icon.
It’s also a good time investment to visit Settings -> Apps & notifications and look for apps with notifications that you don't need. An app like Facebook will have 19 different kinds of notifications so maybe you don’t need all of them? It’s also good to know that Android will ask if you want to mute a notification for all future whenever you constantly dismiss the same notification. Don’t be afraid to say yes because if you change your mind, it’s very easy to turn it back on in apps & notifications.
Apps & notifications is also where you control the default app for different functions such as calling, sms, opening links and different file formats. To change the default app for a specific file format, you first have to find the associated app for that format. It will show up in Recently opened apps if you just used it. Press it to enter its app info -> Open by default -> Clear defaults OR go back and Disable if the former doesn’t work. Next time you open the same file again, it will ask you to pick your default app.
By familiarizing yourself with all these options will definitely lead to less stress and annoyance.