Grief can be incapacitating. While you need to allow yourself time to grieve, you also have to allow yourself to move on with your life.
If you need to, set aside time to grieve for a short period every day. Tell yourself you are going to focus on those feelings and give in to them for a half hour or an hour each day, at a time that works for you. Then, the rest of the day, focus on the daily living of your life.
This way, you are allowing yourself the time you need while not letting it absorb all aspects of your life.