I lost my Nan 3 years ago in November and my Dad 2 years ago in November so unfortunately I know a lot about the grieving process and how horrible it all is.
I found giving myself a challenge particularly helpful when grieving. I think for the initial month or two you need to sit and deal with the horribleness of it all, so trying to get accustomed to 'normal' life again, getting yourself out of bed and through the day. However, after a couple of months of losing my Dad I started swimming weekly which really helped because it gave me something to focus on which had nothing to do with grief, death or sadness. I would try and swim further, for longer, and it gave me a sense of achievement. I know it is difficult to even think about doing something normal but even if it just going out for a walk to somewhere you haven't been before, walking for longer, something really small can help and gives your mind something else to focus on.
Unfortunately, no one really understands grief unless they have been there and even then, people say the wrong thing, assume you should 'be feeling better by now' or 'over it'. I heard all the clichés and trust me it HURTS because of a course a grieving person wants to feel normal and have everything go back to how it was but your thoughts and feelings are all over the place so sometimes you don't even KNOW what you want!
Talking is also useful. You need to get those painful thoughts and feelings out there, even writing them down can help if it is too painful to talk.
My advice is to allow the thoughts, feelings and 'stuff' that comes with grief because you need to feel it and allow it to happen in order to work through it. Bottling things up like I did and pretending everything is okay is not going to help long term. Do not get me wrong, sometimes you have to do this in life but do allow yourself that time to just be. Cry, scream, punch a cushion. Let it out in some way shape or form.
I hope this helps somebody out there x