"A big deep hurt"
One way to understand grief and mourning is like this:
Let's say I walk out to my car and someone has left a broken bottle near where my car is parked. I accidentally trip and fall, with my hand landing right on top of a big broken piece of glass. I get up and I have this big piece of glass sticking deep into my hand. I have a big deep hurt. This hurt is the grief. I didn't want it, and didn't choose it, but it's there and it does hurt. What I choose to do about this big deep hurt is the mourning. I could just ignore it, think to myself, "I'm a big guy, this doesn't bother me," get in my car and drive away with the glass still in my hand and with blood running down my arm.
Obviously, this would not be a good idea. If I ignore this big deep hurt, my hand could get infected, the infection could spread, I could get very sick and I might even lose my hand. It might be such a big hurt that I have to get some help from others to clean out the glass and gravel, stitch and bandage it up, and do exercises to help my hand work all right again. But even if I do all this, I will still have a scar. This scar will always remind me of the hurt I had, and it can also remind me that healing took place to help the hurt get better. If I make some good choices, it won't hurt the way it did in the beginning, but I will always remember it.