Not sure I actually have answers to this, but I am happy to share experiences
I'm not sure that there are generic answers to this, as it all depends on you and your circumstances. Certainly, from my point of view, something I learned very early on was to try to avoid having personal meltdowns in front of my husband. It only happened twice, and I bitterly regretted the effect that my not coping had on him, on both occasions.
I also found it helpful to escape to normal activities occasionally. Even going to the supermarket was a nice distraction. Towards the end I made sure someone else was around if I popped out . If you do not have friends or family to help, there are organisations who can provide sitters - ask your District Nurse for contact details.
Needless to say, this one of the most difficult situations to deal with. Every illness is different, every patient is different as is each partner. Most of would be willing to bear our loved one's suffering, and wish we were carrying their pain instead of them. If you love somebody deeply this is a natural feeling. But one feeling you must not have is guilt. Feel anger, feel despondent and even sadness, but do not feel guilt.
Guilt is self induced suffering that invariably is not justified. Your loved one has contracted a terminal illness that is very unlikely to have been caused by you. So guilt is a wasted emotion.
Meet any anger that you might feel head on. Face it with all strength you can muster and try and work it out of your system. Share it, vent it, kick it about then treat it like it's like something you simply don't need in your life, like a burned out vacuum cleaner.
Sadness is the hardest of all. But you need even more strength to combat this than any other area of being with a terminally ill person. Try not be sad whilst your'e with them. If they are aware of their situation they so often find a remarkable inner strength and face up to the inevitable. If they have, the one thing you will find is that they are themselves very seldom sad.
Try and bring them as much joy as you can muster. Tell them about all the good things that are going on around them, specifically within the family. Tell them of the good things that are expected to occur in the near future, they will want to know.
Terminally ill patients seldom wallow in self pity so try not to show them pity, they don't want it and they don't need it.