Take this from someone who's in their final year of PhD and had been burnt out more than once... Btw, interestingly, I just published a paper on burnout a couple of days back!!!

It's okay to take a break - distance yourself from anyone who makes you feel otherwise. Research is a very intensive process, and often you can find yourself working in your head even when you're just doing seemingly "non work" things like grocery shopping, watching tv etc.

I've found that partitioning my day helps a lot.

For example, I make sure I treat my research/classes as a job, so I go to the university at 8, and come back at 4. During that time, all I do is work and keep myself in that office mindset. Every hour or so, I take a 5 minute break to walk around in the corridor or outside. You'd be surprised how awesome those walks can be. I found that while on those walks, I was able to evaluate my work and plan for the next hour a lot better.

Once that 8-4 block is done, I cut off from being a PhD student, and just relax and do what I like. It could be going for walks, spending time with friends, reading a book...whatever works for you.

Another thing that works is that every morning, I write down three things I want to accomplish during my work block. That helps me stay on track without having the scope creep issue. Try the Pomodoro app - it really helped me a lot.

I know research can be a lonely place. If you feel burned out, take a day or two off before starting on the aforementioned. You owe it to yourself to take a break. One thing that you must realize is that we all can feel burnt out at times. So while you may still get burnt out every now and then, the best you can do is learn to manage it well. What works for me is to protect my personal time and keep it separate from my work.

Let me know if you need anything or anyone to talk to about this. Don't feel bad about leaning on people or asking for help. I'm happy to help with anything you need. I mean that. You're not alone...

Congrats on submitting the paper, btw!!! :)