The best way is to just accept your grieving process. Accept that you are feeling things and accept your reactions to those feelings. that's extremely hard, i know. You probably just want to distract yourself instead of dealing with the elephant in your brain. But being upfront with yourself and your feelings really helps.
Maybe, instead of longing the past, celebrate it. Instead of bringing yourself down because you don't have them anymore, remind yourself of how lucky you are to have had that person in your life.