[reitanqild]

My possible #1:

I am afraid that I will will be interrupted before I get anything done.

If this is the case: don't work from home unless you live alone or with understanding people, put headset on, turn phone off (or only sound for trusted allies) etc.

Make trusted allies, but be careful: I recommend framing it as a matter of being more effective and reaching flow state quicker instead of framing it as impediment.

Edit:

As others have mentioned: pomodoro. I'd also like to mention the autofocus system by Mark Forster.