If you like being around other people, talking with patients, and actually thinking rather than memorizing, third year is a welcome change. For me it was a definitely not stressful. There were some trying moments, but nothing that had me at my wit's end like first and second year did. And it's more time consuming, but again, at least for me, in a good way - I no longer had to fluctuate between feeling guilty when I was doing anything that wasn't studying and absolutely hating life every moment that I was studying. As a third year when I left the hospital, I knew that at most all I had to do was read maybe an hour (or most nights, not read more than about 15 minutes) and then the rest of my time was my own.
The biggest thing to realize is that as a third year when you're in the hospital or clinic, you don't have control over your schedule. During M1 and M2, if you don't want to go to class, you don't. If you do decide to go to class, does it matter if you show 15 minutes late? Do you want to take 2 hours for lunch? Go right ahead. Do you want to study for 5 hours tonight or 7? You choose and where! As an M3, you have to be where they want you, when they want you, and it doesn't matter if you're going to sit there for 45 minutes doing nothing but watching the resident update their facebook, you still have to be there. It's a tough transition for a lot of people to give up that freedom, but not being in control of your schedule is a fact of life from the first day of M3 to the last day of residency...and probably well beyond depending on the situation.