I think it depends how you do it. I'm not an expert, I just talk about my own experience.
For me the 'fastest' way is to hike alone seven days in wilderness without meeting anyone and not staying still in one place. Having clear physical task helps to settle things.
First time I did it, I think the one of the biggest revelations came in the morning of the 5th day. I was really unhappy. Never been outdoors long time. I was tired and dirty first 4 days. Everything I did I hated. I hated walking. I hated putting up a tent etc. and did everything sloppily and as little effort as possible. Then just woke up at one morning and there was no internal bitching. I had to cross a tiny river, undress and go into cold water and carry things over. I just did it without thinking or aversion. I just took the shock of cold and horrible slimy feel in the mud without flinching. I was not assessing my performance or proud of my new stoic style of doing stuff. It was not fun but it was very peaceful and matter of fact.
I have lived in a hut for a few months in a summer in constant isolation with nothing to do and the idleness brings up weird mental states. Like several days of vivid fantasizes followed by sleeping a week 9-10 hours day with weird dreams and being little paranoid. Creativity bursts where you think you are very close to some breakthrough were the worst. The urge to do abstract carvings or build gadgets could get out of hand for me. Eventually things settle down at least for me.
