Though I am glad you are feeling a bit better but if you ingnore your previous feelings then they will come back with a vengance.
I have been to therapists (all are not created equal) and though it seemed to be a complaining session sometimes, there were a few times that I did have an enlightening thought or understanding. Like the light bulb being turned on.
The mind is a wonderful and highly complex thing. It sounds as if you have had these recurring "sad times" and that sounds like there is an issue/s underlying that bother you greatly and yet have either put it aside or forgotten it. There were a few things that I found out in sessions that did not make my "problems" go away but did make things easier to understand and therefore not feel so bad. A few of those and life got to be full of speed bumps instead of mountains when things were not going well or mood was off.
I often feel that I have done little right with my life though I do have a relatively good life...everyone has their idea of that. Hindsight is 20/20 and to be honest, I like things to go the way I want but can compramize.
No matter what others think, if you feel a way, it is real.
Meds too....don't anybody jump all over me..but, don't discount the proper medication. I hate to depend on something like that but if it makes life semi enjoyable compared to wanting to crawl in a deep cave and stay there....
This may sound goofy to some people but I am learning that my moods are partially dependant on some of the food I eat and chemicals that are around. Some people are more sesitive than others. I didn't take that idea seriously until my young one started having unexplainable mood crashes. Yes, kids will be kids, but if we avoid certain food and environmental stressers, there is a huge difference. We have tried this approach again and again and do see the huge difference. Some is allergies and some are not...maybe just sensitivities???
I have totally hijacked the post so will stop soon. I just want to let you know that so many of the things you said in your original post made my chest burn and get red in the face. I really identified with it. There is something wrong and if you don't find out what then it will be hard to change the way you keep feeling. Sadness and disappointment are a fact of life but the dispair you feel is not/should not be.