I'm so sorry, OP. 
Weirdly, for me, I think understanding that the grief isn't an abnormal reaction that needed to be fixed helped. I was supposed to be sad, I was supposed to be hurting - they were signs of a normal grieving process, and of the love I had for someone, and I decided not to spend too much time trying to make it 'go away'.
If I got that 'hit by a tidal wave' feeling one day I didn't immediately go and distract myself with something else, I just kind of allowed myself to go, oh I'm really really fucking sad right now and I just want a minute to sit in this sadness and think about the person who's gone and BE sad about it. That made it so that grieving, even the most raw and unexpectedly painful parts, became something I was living with, not trying and failing not to have. It made it easier for me to feel like I could handle it: yes, I was very very sad, and yes, I could keep going anyway, rather than feeling like it had stopped me in my tracks and I couldn't on with my day/week/month/life until I didn't feel like that any more.
The 'not there any more' is a weird one, isn't it? It doesn't seem like it could possibly be true that someone so important to you just ceases to exist. When someone very close to me died, I read this at their funeral and it made that part feel less scary and sad to me: You want a physicist to speak at your funeral...
And finally - the most annoying, boring, answer, but time. The stop-and-catch-your-breath painful moments come less and less often, you can hear their name without it feeling like a kick to the stomach. Then there's maybe a period where you forget a bit more, for longer periods, for a while - and it's nice because it's not all-consuming, and then the guilt of forgetting hurts a LOT again, but you realise it's starting to heal.
My therapist describes it as a old injury (a slightly gory but apt metaphor I think) - for a while when it's fresh, every time you knock the scab off or rip the stitches by thinking about it or being reminded, you open the whole wound again and it bleeds and it hurts a lot. Then after a while, it starts knitting itself back together and it might still be painful but it's less so, most of the time, but if you really poked it it'd hurt, or re-open slightly. And then, eventually, it becomes a part of you that's not the same as it was before but it's still there, and it might occasionally twinge but you've learned to live with the scar.
You get there eventually. Be gentle with yourself in the meantime, and let it be what it is - if it hurts, it hurts. It doesn't need fixing, because it's part of the healing process.