There are five stages of grief in the Kübler-Ross model. I’ve sourced the stages from Wikipedia.org and shortened them where appropriate.

1. Denial — The first reactions is denial. In this stage individuals believe the diagnosis is somehow mistaken, and cling to a false, preferable reality.
2. Anger — When the individual recognizes that denial cannot continue, it becomes frustrated, especially at proximate individuals. Certain psychological responses of a person undergoing this phase would be: “Why me? It’s not fair!”; “How can this happen to me?”; ‘”Who is to blame?”; “Why would this happen?”.
3. Bargaining — The third stage involves the hope that the individual can avoid a cause of grief. Usually, the negotiation for an extended life is made in exchange for a reformed lifestyle. Other times, they will use anything valuable against another human agency to extend or prolong the life. People facing less serious trauma can bargain or seek compromise.
4. Depression — “I’m so sad, why bother with anything?” […] During the fourth stage, the individual becomes saddened by the mathematical probability of death. In this state, the individual may become silent, refuse visitors and spend much of the time mournful and sullen.
5. Acceptance — “It’s going to be okay.”; “I can’t fight it, I may as well prepare for it.”; “Nothing is impossible.” In this last stage, individuals embrace mortality or inevitable future […] this state […] typically comes with a calm, retrospective view for the individual, and a stable condition of emotions.

In my experience, this isn’t a journey from 1 to 5 without ever looking back. There are good days and bad ones. Some progress through these steps slowly, while others go faster. It’s completely normal for it to take a year to progress through these steps. Especially if each new holiday or special event brings another painful experience.

As the parent, especially the primary caregiver, you are likely to proceed through these steps faster than others around you. You may even proceed through them faster than your spouse. It’s normal to have accepted your child’s medical condition when everyone around you is still struggling through the above stages. It’s also normal if you take longer than everyone else to accept it because it’s front and center every day of your life. Everyone goes through this journey at their own pace.

There is no one thing I can tell you which will help you reach acceptance. It’s not something you can pretend to have reached. It comes with a significant amount of inner peace. If you’ve reached it and others around you have not, you may be accused of not caring or giving up. This isn’t the case. You’ve simply come to terms with the fact this is your new reality. You’re going to plan and prepare as if it’s here to stay, and no longer feel the need to fight the inevitable. You’ll still advocate for your child. You’ll still do everything you can to make them more comfortable and help them overcome whatever obstacles are in front of them.

If one of the earlier stages sounds more like where you are, don’t fret. Keep in close contact with your support network. Know that things get easier to manage with time, even if they don’t get better.

…give us the serenity to accept what cannot be changed,
The courage to change what can be changed,
and the wisdom to know the one from the other.
– Reinhold Niebuhr (1892-1971)