1) Devices or people
For both of these, "blocking" is the way to go For people of course this should be more of a request.
2) Other things racing in your mind.
Generally the result of your not tracking all your open loops effectively, the solution is just to jot down in your notebook or task management system whatever the open loop you're thinking about is/needs done about it. It is absolutely key you review this list often enough that you truly trust it.
3) The task itself
In the words of David Allen, author of the life management system Getting Things Done ™, "you're more productive when you're relaxed." In so far as it is the task itself that is distracting you, relaxing and looking at it objectively is a massive help. If needed, take just a second to compare it to a circumstance like being in a war just to make you realise you're actually pretty well off right now and what you're facing isn't so scary.
- How long should your deep work be?
- How do you say no politely
- How much time do they spend deep in work?
- What online resources do you recommend studying?
- How do stay focused while working, with out opening other tabs or your mind wandering?
- How do you stay focused for 4 hours?
- What is your favorite way to study?
- How can I focus on these days when I have absolutely no motivation to do anything and I feel tired?
- What is the best way to study for a big exam?
- Typing or writing? Which one do you like best?