People talk about "the stages of grief". The most well-know model is probably that known as the Kubler-Ross model. I don't actually know too much about the model. I do know that labeling things as "stages" seems to imply an ordered progression through grief. That isn't at all what it is really like, of course. I can identify with some of the things labeled as stages, but there is no progression. And, for me at least, I jump all over the place and revisit many "places" I have already been.
Currently I'm experiencing something that I can only explain as panic attacks. Most of the time there isn't anything specific I'm tense about. I'll just be going about my business and my heart will begin to race, my stomach will turn over like people describe as butterflies and I'll feel something like extreme tension that comes from stress. It is like nerves leading up to public speaking multiplied by 1000. Sometimes it just comes on out of nowhere, but when that is happening I can be sure that uncomfortable work situations or other interactions (with family or otherwise) will set it off. I felt this way for about 2 weeks last month and then it went away. Now it is back. And it sucks. Big time.