I feel Ph.D degree is not painful to a student and mentor as long as proper understanding b/w their relationship exist. The relationship starts from common understanding b/w them about the topic chosen. The rest is purely depends on the scholar, if scholar ready to commit his work, dedicate his work sincerely to the chosen topic. Then, the rest is very fruitful to both student and mentor. Mentor always ready to help his/her students, so students need to understand that go ahead with dedicated work then Ph.D degree is easy going for both..ok all the best..
My supervisors advice was Nike ' just do it'. Another colleague said to do a PhD you have to suffer pain. If you don't suffer pain you're not working enough. He never got any PhD students
Doing a PhD is the most painful experience. However, if you have a good mentor and a topic that you are really interested in, the journey becomes more interesting.