My advice is the plan and diarise your action points. I also journal what has been done each day so I can reflect on my progress. Finally when I feel lost, I revert back to my question or title to ensure I'm staying on track.
I was fortunate enough to be trained by a journalist at The Economist who helped me identify the best time of day when I was most productive. This varies for certain people, but working to your circadian rhythm feels more 'natural'. Other tips involve removing distractions, getting your thoughts on paper without trying to make it perfect, and having an accountability partner who can also offer some constructive feedback.
One Piece of advice I would give would be to write a conversation about the topic. I would imagine I was telling my mom about what I just learned and how it will contribute to making the world a better place. Editing software can help the papers structure or verbiage but the conversation is there in the paragraphs. What I know, what my professors know, what is new and what is yet to be discovered or needs to change. Staying engaged becomes easier because you are putting the conversation on paper. You are committed to the task because you are passionate about the subject, not necessarily the topic. And at the finish line is another step closer to a life goal.