It looks to me like it's possible to resist grief, at least to some extent. I think people do it all the time. And I think it's an error to do so.

It is only an error if it continues on too long. Avoidance in most circumstances is a natural and innate part of the process of dealing with grief.

Avoidance is sometimes an adaptive strategy in coping with adversity and sometimes maladaptive. In the case of bereavement, experiential avoidance usually plays a role in facilitating the healing process. The emotional pain associated with new information that a loved one has died is so severe that people need time interspersed with periods of respite in order to be able to fully acknowledge the unwanted reality. Respite can be achieved using cognitive avoidance, and sometimes by also avoiding contact with triggers of emotion. When avoidance is used adaptively, it facilitates processing of the painful information as well as restoration of the capacity for a satisfying ongoing life. As processing and restoration are achieved, the need for avoidance diminishes and the strategy must be relinquished. If it is not, or if avoidance is over-used in the wake of bereavement, the strategy can backfire. Processing difficult information is impeded rather than facilitated and acute grief is prolonged. (Shear, p. 357)

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I could instead turn my mind to the pain, and look at it in exquisite detail.

This sounds potentially dangerous to me. You could easily retraumatize yourself or deepen your grief by doing this. It is probably best to try to do this when with someone else and also not too early in the grief process. This does not mean that you should never do this, however, as this is something that has to happen eventually.

The feelings from grief have an undulating or wave like motion. There will be times where you can face your feeling and times when you cannot. This is totally fine. It does, however, become important as more time progresses for you to make sense of the loss and find benefit in it, which fortunately often becomes easier as time progresses:

Those who were able to make sense of their loss typically did so by seeing the death as predictable or as a natural condition of life or by suggesting that the death was comprehensible within the context of their religious or spiritual beliefs. On the other hand, those who were able to find benefit in the experience tended to report that they had learned something important from it, about themselves (e.g., that they had the strength to cope with the adversity), about others (e.g., the value of family and relationships), or about the meaning of life (e.g., learned what is important in life). (Davis, C.G., Nolen-Hoeksema, S., & Larson, J. p.570)

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I think the first three so-called "stages of grief"

I don’t think these stages are currently accepted anymore as they are seen to be too rigid. See here for some recent developments on the understanding of grief and bereavement.

It required a choice, every moment, to keep my focus on what hurt rather than on how much it hurt or how unfair things were or any other story that decreased the pain I felt in that moment. And it was tiring to make that decision continuously.

I think the power from this actually comes from the perspective that you are taking on the loss rather than the simple fact that you are thinking about it. For example, I think there was a big benefit from not thinking about how unfair it was.

In summary, I think your post is describing something that should happen in the later stages of the grief process. It might also not be suited for people with avoidant attachment styles. There is no doubt that they are some ways to do it better than others, for example this looks pretty good. My opinion, though, is that if you were trying to find out how to handle grief well, then it would be more important to look at things like what your strategies are: to handle it, to seek help from others for it, to compartmentalise it, to challenge the unhelpful thinking it will induce etc. See here for more.

P.S. can you please add a summary break somewhere in your post.