Speaking for my own experience only:
I attended a research-focused clinical Ph.D. program. The first few years were the most challenging, as this was when the coursework was most intensive, my research was just getting off the ground, and the learning curve was steepest for clinical work. Because I was learning and doing a lot of new things at once, I had to focus on time management like never before. Neither in college nor in the couple of years I spent in full-time employment afterward had I ever had so many responsibilities. It was a lot of work, but in truth grad school was not a bad way to spend most of my 20s. I still had time to socialize and pursue outside interests, though there were also long stretches of time (weeks or months) when I had to put those things on the back burner. 12+ hour days were not rare, especially in the earlier years. Through it all, there was only one year that even approached "soul-sucking," though situational/chance factors played a significant role.
Throughout graduate school my default location was my advisor's lab. I worked there on my advisor's projects and my own, taking breaks to go to my classes, clinic appointments, etc. and then returning to "the office." I treated it like a full time job, so I usually went in early to get a jump start on my day. There was a social side of belonging to a lab with 2-4 other students, depending on the year. Though we all had our personalities and quirks, for the most part we were supportive of one another. My identity was tied more to my lab than to the student cohort for my year. Depending on where my funding was coming from in any given semester, I spent a portion of my time either being a TA or being an RA for my advisor, but in the year before internship I received a competitive fellowship and I could hone in on my dissertation. For a couple of years I went off campus a day or two a week for practicum, which intensified the time management demands.
Hope that helps... happy to answer specific questions if you are looking at this type of training.