When you work in a field in science, such doing a PhD, how to keep focused and prevent procrastinating?

I try to "chunk" my time to focus on one task at a time. Also, as counterintuitive as I may seem, making sure I take true, restful breaks really improves my energy and stamina, which helps improve focus and prevent procrastination. In such an intellectually challenging position it's better to take breaks to work at your peak efficiently than to push through and make mistakes. Be kind to yourself and celebrate what you do accomplish. Theres always more to do but recognize how far you've come to stay motivated. Good luck! Take care of yourself.

I put my phone in do not disturb, use Windows Focus Assist, and I start every work day with a minimum of 15 minutes of dissertation work no matter what else is on my plate that day.