There were multiple times in my life when I thought I was at the lowest, and the first one was shortly after my husband and I immigrated to the US. Our situation was truly awful, but we met a lot of recent immigrants at that time, and the one thing I got out of it is that there is always someone who is worse off than you are, no matter how bad you think you have it. That has stayed etched in my mind 20 years on, and I still truly believe it, and it gives me strength, and cures me of complaining disease.
My last lowest point was really low. I have a mood disorder that amplifies everything and makes bad times even worse, so I had an added blow from that, but even without it, it was really low. I had realized that my marriage was actually awful and abusive, and that I had somehow completely missed that fact, I don't know how. Blind? Delusional? This was after my first child was born, and I also had health problems for 2-3 years after that, with 4 separate issues being life-threatening, and a whole lot of more run-of-the-mill issues. I got no compassion from my husband. I had a horrible post-partum episode during that time, where some medication side-effects affected my ability to work. The inability to get work done was a big blow from the personal worth point of view. But from the practical point of view, it was a hair-on-fire emergency. My husband had been unemployed for years, and I was the breadwinner, and I was on verge of getting fired. If I got fired, I would have lost health insurance, so couldn't get treatment and would have never gotten better. I knew I would have never gotten another job then, because I was in no shape to interview, so prospects were bleak. I had visions of us living under a bridge. I had to hold on to that job, because that was the only option. I had been coming off of years of severe sleep deprivation, and was really unwell, and my doctor kept saying "take weekends off, you need to rest if you are to get better", but I worked every day, all day, weekends... at, like, 30% productivity, just to get things moving until I get better (and very slowly, things did improve). In the midst of this I got pregnant (unplanned), had some complications, and the pregnancy ended at 24 weeks, that's well past half-way. This was preceded by a very high-stress, low-sleep fortnight of making life-and-death decisions, and followed by my husband swearing that he would never have another child with me 'because I was the worst mother in the world'. Now, I may not be mom of the year, but I know I'm not the worst mother in the world. He knew I wanted more that one kid - that statement was just meant to hurt me. The abuse is ongoing, I don't want to get into the details, my daughter is getting visibly stressed over it, but I'm not yet able to manage employment and single parenthood. I try to fix marriage, which cannot be fixed, until I just break one day. It is really, really depressing to realize that after all I have accomplished (and I am very accomplished), I just don't matter to the father of my child. I was truly, deeply, deeply, unhappy during those years. I wasn't 'really' suicidal, because I had a child that I knew my husband couldn't take care of on his own (and we have no family here), but I thought of death every day, for years. It went on like that until I figured out, one more time, that my husband does not love me or care for our relationship, and I just broke. I tell people that I've 'used up my stress minutes'. I just couldn't stress any more. Nothing mattered any more. It started with realizing that I wouldn't be upset if my parents died, and it just progressed from there. I couldn't have been shook up if one of my kids got sick, or died, because that's just life, and we move on... It was actually a reprieve of sorts, so it didn't feel bad, I just felt dead. I didn't care, and I didn't care that I didn't care, and that was alarming.
However, that was the turning point. Once I gave up on my marriage and my abusive husband, my life opened up. I focused on my work, on things I could do. I decided to stop trying to build a partnership with someone who is oppositional just out of spite. I told my husband I was stopping birth control and that he can do whatever he wants with that information. We had another child and I was happy. I looked back on things I have accomplished that far, and it doesn't have to be school or work, just personal victories count, and I realized that I was awesome, and that was enough for me to build my sense of self-worth. I had a big shift from depending on outside validation to finding it within myself. I KNOW I'm awesome, whether others agree or disagree. This may sound like some great choices I made, but really, I clung to dysfunction for as long as I could. When I could not any more, I set myself free. Somebody smarter, or less needy, would have moved on sooner.
I got a couple of things out of that. The first is my self-worth, and a true sense of happiness. I am truly, deeply happy now. I had very carefully weighed some choices (whether to divorce, whether to have another child), knowing myself, and knowing what I could and could not live with, and it paid off. I highly recommend that. I found a quote by Theodore Roosevelt: "do what you can, with what you have, where you are", which was tremendously liberating, and I hold it dear. You can only do your best, and there's no reason to stress, because that only decreases your productivity, and you actually do worse. Also, my physical health improved, my mental health improved, I went back to my old level of productivity, got promoted at work, got a raise, and I feel as secure at my job as one can realistically be. The second thing is that I will never despair again. I have been at the deepest bottom of objective hopelessness, and yet, unbelievably, my life turned around, and I got what I wanted, and I am happy. It doesn't mean that the next time it will turn around, but now I know that even impossible is possible, and there's no room for despair. It's helped a few times since.
As for the times when I had to keep going because I had no other choice, one day I came across magnets with two of Winston Churchill's quotes, which I hung in my office, for those days of 30% productivity. One is "when you're going through hell, keep going", and the other is "never, never, never give up". They are still in my office. They probably puzzle people who come in, as my life is pretty calm right now, but they're staying. :)