'It is often said that those who have the happiest and most loving relationships move on the quickest after the death of a partner'
By whom? I think problems can result when there are particularly young children involved, or children at home, IME.
My most intense experience of bereavement comes not from losing a spouse but my child. Even in the early days of that loss, I was, being an adult, acutely aware that this bereavement was different for her two surviving siblings, and still am so. And I do temper my behaviour to account for that fact, and have also sought out as much support as I came for them in their bereavement and loss. Because being a child and a child at home leaves them with far fewer options than I have and far less capacity as they are not neurologically developed to adulthood.
As a result I have had to swallow down and suck up a lot, but hey, that's part of being an adult and being a parent. It's realising that your own feelings, your happiness, etc do not exist in a vacuum and that your own actions have serious effect on other people, particularly young ones who do not have as much capacity as I do and far fewer options.
One thing really stuck with me. We house sat for a very dear friend about a year after our daughter died, and this friend's lovely carer came to visit and, being qualified in childcare and working on a child-related degree, offered to babysit for us and allow us time alone as a couple. But she also told me of how her own father had been killed in a RTA when she was 11, and how much support she needed and thankfully got, as her grief was much different from her mother's, understandably.
And again from my friend, as her mother moved on very quickly, marrying another man months after her father died and blending the families immediately, had an absolutely detrimental affect on her and on her relationship with her mother, which has never been repaired. Now my friend is a mother herself, I saw her last Summer. I did ask her about her bereavement of her father, and her relationship with her mother, as she invited me to. We are both now in our late 40s. She explained, that even now, she feels her mother was terribly selfish to have done what she did, as she had no space to grieve her father's death, she was too young to go anywhere, she was trapped in a blended family and told she was selfish for begrudging her mother happiness after her father's death. But as she explained, 'What on Earth was I supposed to feel?! I was THIRTEEN!' She is now the mother of a teenage girl herself and says she cannot imagine doing such a thing to her own child, no matter what the cost to her personal happiness. 'You have to put your kids first, don't you? At least while they're at home, surely? They don't have anywhere to go. It's not like they can tell you to fuck off and go out and get a job, can they? It's all well and good saying well they're dead, not coming back, life moves on, but it moved on too quickly for me. I was not given space to even register that my father was dead until I was told to accept Jack and his three kids.'
It didn't end well for her or her siblings. Their mother was an inherently selfish person who put her personal need to not be single and have a partner before their own need to grieve for their father.