I've lived abroad for 20 years. It's been an experience of contrasts: Totally heartbreaking, but has given me so very much.
I actually didn't really want to go; I followed my husband back to his own country. He was desperate to return, and I thought it seemed like a cool enough adventure. It's worth pointing out that I had NO idea he'd been born abroad and raised there until he was 9 when I first met him, because he'd lived in England for 26 years, all his family were in England, and he had no foreign accent. His mother is English. Anyway, he became very disenchanted with the UK, so we moved.
It absolutely broke my heart into a million pieces. I am not one of life's travellers. I like being at home and I love England. However, perhaps it's a good thing that me falling in love with my husband made me do it, because I'd never have done it on my own.
I have discovered that I love where I live now, and I have certain failsafes that I couldn't have in Britain, like specialist medical treatment for a rare condition, and certain insurance products that the UK doesn't have. My chosen field of work is also much more accessible here - not stuck with London like at home. I prefer the weather here and I find the people friendlier than in the UK.
But, my parents both went through long cancer journeys, and it was extremely hard. When I made the choice, though, I knew I would live many decades after they had gone (hopefully), and therefore didn't want to miss out because of them. We visited each other quite frequently and stayed for at least two weeks each time. As it turned out, my mother only lived for seven years after I left anyway, dying at the relatively young age of 70. I'd probably feel I'd missed out on a lot more if she was still alive and kicking all these years later. She'd be 82 now.
My marriage did break down, and that was also hard. But I have good friends here and am very close to my sister back home. We message constantly.
I might have moved back if I still had Mum. But I'd have to work in London on a much lower salary than here, as the industry is less well-paid in Britain, I wouldn't get the right medical care for my condition, and I wouldn't have the peace of mind that I get with my various insurances. So it would be a very difficult thing to do. With my specific set of circumstances, I'm safer and better off where I am. But oh, do I miss England and the food and the rain and the sense of humour. So much.
Moving abroad has been the education of my life. (I don't want to say where, as it's too outing.) I absolutely appreciate what we have in the UK in a way I never would have been able to otherwise.
I do think that the most serious danger of moving abroad is that you can get stuck there if you have kids and the marriage breaks down. I had NO idea whatsoever of this terrible trap when I followed my husband. As it happens, I ended up not having kids, so I'm not actually trapped. But I know someone from home who is trapped here, and it's not good. The children will be adults very soon, but they were born here and have their lives here. They are not culturally English. So if my friend wants to be a part of their lives, and her eventual grandchildren's lives, she'll have to stay too. This is how you get trapped: You end up with foreign children who only have a tenuous connection with the UK. I know another British family here who did move back to the UK, but they left their university-aged daughter here.
TLDR: It's a complicated experience of great highs and lows.