The dog days of graduate school as a science PhD candidate can be dark. After coursework, teaching, qualifiers and candidacy exams, you have an unobstructed view of the "Great Divide" that stands between you and completing a PhD. You continue down into it with some optimism. But eventually, you trip and fall head first to the bottom. Then it's been days since you've seen light or showered. None of the attempts to crawl out have gained you any ground. To top it off, your advisor yells down into the chasm periodically, "What have you done for me lately?"
Maybe it's not that dark, but the slump after the second year is something we all feel. It can be very difficult to get past this. From someone who has been there, a few realizations really helped me.
Your health comes first. Yes, your thesis work is your baby, but as Mom, you can't take care of it without taking care of yourself. Go to SLEEP. It's so important. Take the time to acquire and eat adult food (ramen and vending machine staples don't count). Try to get exercise. How all of these things make you feel will make up for the time you "lose".
You must keep a life going outside the lab. This can be time with your group of friends, reading for pleasure (not work!), or some other hobby. Just keep something else on your plate. Realistically, you can't have it all. Going out 4 nights a week, taking a phys ed class, and being part of every club you can find is probably not a good plan, for example. Prioritize, and give yourself something to look forward to.
Look around! Others have been where you are. It can help a lot to talk with more senior members of your research group. If going outside your research group will allow you to speak more freely, reach out to other students in your program. Everyone has had some graduate school trials and tribulations. Other faculty can be good mentors, but be prepared – they likely empathize more with faculty at this point in their career.
Unfortunately, life can still feel a bit hollow if things aren't moving forward in the lab. I've found that my satisfaction, and as a result, the energy I bring to my research depends strongly on whether or not I'm learning. This drive to learn is probably why we ended up in graduate school. Everything can go wrong (as it often does in science), but I will feel ok if there's one interesting or insightful thing I can gather from the day. So I found a way to create that. One day, rather than listening to music, I started a podcast. It was refreshing to hear about something, anything other than my field. I was learning. I could do it while working at the bench. I had things to talk about (other than failure). It was great.
Keep a schedule. Breaking down a giant task into short term goals makes it much more manageable. Use those short term goals to create a schedule. This allows you to have direction and realistic expectations rather than frantically trying to do everything at once. Many students don't plan, try to do too much at once, and then spend extra time redoing those experiments. Pace yourself. You're going to be here a while anyway.
All of these things helped me begin to crawl up the other side of that "Great Divide". When I lamented the slow progress, a mentor told me very casually "most thesis work happens in the last two years anyway." I was floored. Apparently, the progress was not so slow after all! So cheer up, and start writing that thesis!