I moved state about 14 years ago for a fresh start and 'sea change'. I have a bipolar diagnosis now but at that time I was being treated for anxiety and depression alone. I didn't know it at the time but it is now clear that I was in something of a manic state when I made both the decision and the move. I experienced initial exhilaration with the move but soon ran into difficulties. Some of these were unavoidable life events that would have arisen in the old place too: the death of my father about six months after I left my previous home town; physical illness that meant I needed surgery; and financial difficulties. Being away from my old place when these things happened meant that I had less personal support and wasn't able to be there for my father as much as I could have been if I'd stayed.
Some of the difficulties were related to the move excacerbating my mental illness. Even though it was only a move from one Australian state to another, I experienced a kind of 'culture shock' in the new place. In the old place I had many friends and a vocational focus that fell away for various reasons in the new place, where I had trouble finding a social 'niche' and new friends. It was also a new relationship that partly brought me to the new place and that fell apart badly within a year of arriving. Some of the problems I encountered in the new place continued on for years.
Now for the good news. I am still in the new place and found a new and long lasting relationship after the first relationship broke up. We have been together now for 12 years. I don't have as many friends in the new place as I had in the old but some of the friendships in the old place were really fairly superficial and the ones I have made here are on the whole deeper and more meaningful to me. One friendship here in particular has been the closest I've ever had in my life. The 'sea' part of the change has always been wonderful and I have walked endless kilometres along beaches over the years, bringing a fundamentally greater peace of mind to my life. I would find it very difficult now to move back to where I came from as I have come to love this place, though I still have my struggles with MI.
I tell this story in some detail because, really, a decision and move like this is going to be a different experience for everyone, depending on circumstances and nature of MI. However, there is a saying that seems relevant to all cases: 'wherever you go, there you are'. To me this means that wherever we take ourselves we are going to have to deal with our own personal issues no matter what. I would neither encourage nor discourage a move like the one I have made. There have been pros in cons in equal measure I would say. My main suggestions would be to make the decision in a calm and rational state if possible, take time before making the move, don't expect a move to fix personal issues that you will carry with you wherever you go, and factor in that there are likely to be some real difficulties in adjusting to a new environment. If the move still seems worthwhile after considering the specific issues relevant to your circumstances, I'd say go for it. My best wishes to you either way.