Everyone is of course different
My mum died 18 months ago. She had pancreatic cancer and at presentation had an 8 cm tumour so we expect 3-6 months. She was lucky enough to get on a trial and lasted 20. In that time we did loads of building memories etc which helps a lot.
I think it can help to plan and anticipate. I thought about the things that might bother me - I didn't want mum wrapping in a sheet etc after she died and wanted her to be peaceful.
I was lucky that mum talked to me a bit about her wishes too. There are essentially 3 bits:
Immediately after death - family numb and a bit shellshocked. I stayed with hospice staff and we cleaned her up, took locks of hair and I got a posey of fresh herbs from garden (she hated cut flowers). I made sure she had her glasses on (sounds wierd but she wasn't mum without her glasses )
That bit helped me and the others know she was dignified and comfortable
Next is "organising mode" - even if your brother is executor and we'll organised there stuff you might want to do. Getting registered and a funeral booked are fairly straightforward tasks.making sure you mum eats something, planning the funeral content a bit different.
Mum had left us some hymns and poems etc and we all sat down with the vicar and planned the funeral. Sounds stupid but we did her a fab job - she didn't want us to weep so we didn't but had bright flowers and funny stories. His worked because we knew it was what she wanted - can you talk toy our dad and find out any strong wishes? (I know not everyone can)
The last bit is much much harder. You catch yourself walking rind the supermarket wondering why everyone seems so normal - don't they know your mum has just died? How dare they be tasting cheese or comparing washing up liquid?
It stings. You wake up feeling normal then just as you are brushing you teeth you remember. There are tons of tiny reminders everywhere you look. For me what helped was:
- knowing I had done everything I needed to with mum while she was still with us
- knowing we had carried her wishes to properly after she died
- giving myself permission to be sad if I needed to but also holding myself to account a little - its not ok to be mean to my husband today just because I feel sad (I hadn't anticipated how sad it would make him - that's a whole different thread)
- knowing the key dates would be wierd and allowing that I. E birthday, Christmas etc
Time does heal. You don't stop being sad it's just life creeps back in and you do start to taste cheese and compare washing up liquid again. And amazingly you get through it.
If you are really struggling then local bereavement groups, the hospice, CRUISE (bereavement counselling services) etc can help. But so can a good mate and a bottle of prosecco.
I also found some motivation to sort bad habits out (used the fact mum told me to look after myself as motivation ) so lost 3 stone and ran a 10k. That ultimately helped me get pregnant (was struggling) so now have "baby due and mums not here". It never fully goes away but I know she'd be proud of me 
Have some 
or
- whichever suits