My deepest Sympathies to you and your family.
It is always very hard to lose someone you love, and even harder when you were their caregiver for so long... My mother and I were both caregivers to both of my grandparents the same as you...Take one day at a time it is hard to adjust, but in time the pain you feel today will slowly go away...
My grandparents have now been gone 11 and 13 years and I still find myself picking up the phone to talk to them and realize they are not with us.
Just know that each day it gets a little bit better
Always Remember the love and good times that you shared with them, and they will live on in you!!