All of these people face somewhat similar circumstances.  If you find yourself in such a situation, here are some suggestions to help you get through the process.

1.  Shock or relief.  The first stage, after at least one spouse decides to leave the marriage, is shock, if the other spouse somehow isn't expecting it, or relief, if the spouses have been discussing the decision openly until one or both commit to ending the marriage.  It's a difficult decision for so many reasons.  Once that decision is made, both parties need a little time to let it sink in.

2.  Fear.  A common second emotion is fear about the future.  Past plans come undone.  Finances get stretched thin and new arrangements need to be made. The need to work may put off retirement and will affect spending.  Relationships with grown and nearly-grown children may change and will probably be a little awkward for a while.  So many things that are taken for granted suddenly have to be changed.  There's a lot to be concerned about.

3.  Recognizing opportunities.  With the changes comes some new freedom to change course and try something new. Most people at 50 will still have 30-40 more years to live. You can move to a different job or another town or a new neighborhood.  You might downsize and streamline your life.  New hobbies and activities are possibilities.  You can also make new friends.

4.  Start with small changes.  With so many new and different directions you can take, don't go crazy and completely start over.  Generally, you will be more comfortable with adding small changes at first and then making bigger changes as you get used to new arrangements.  Everyone needs some stability which can come from some carryover aspects of your life.  Especially -- Don't rush out and get remarried.  Take your time and get to know the person.  There's plenty of time!

5.  Expand your horizons.  Use this opportunity to try completely new things that maybe you couldn't do while you were married.  You don't have to re-create your old married life.  Try some new interests and make some new friends.  Take some classes.  Reconsider your assumptions about how you want to live your life.  This could be the beginning of an interesting new life.  If you don't want to do a lot of new things, you still can have a fresh start to some old activities.