It's self-reinforcing because if we can change our negative thoughts, then our feelings will change. If our feelings about what we must do change, then our thoughts and feelings about ourselves will change. I guess that is progress. Solitude allows us to develop our inner resources and feelings of independence. Focus on the humorous aspects of daily caregiving - and I know there are many if we allow ourselves to look at things that way.
Laughter is therapeutic.
Talk to yourself in positive ways with upbeat messages instead of the negative thoughts that make you feel lonely and depressed. Try hard to let go of what was so you can appreciate what is. Be patient with yourself. It's hard to change patterns of thinking - especially when we have so many reminders of how tough caregiving can be. Keep working on it.