I haven't done ketamine, but I have experimented with dextromethorphan in the past. Both are classified as dissociatives, but ketamine is much stronger.

On DXM, I tended to "feel the love energy of the universe" which was a very positive experience when I was depressed and unmedicated. It did have some effect the days after, but nothing terribly long lasting because I was still chronically depressed.

Something that did help reduce my depression for a noticeable amount of time was doing a mix of psilocybin mushrooms and LSD (aka hippy flipping). In the weeks afterward, I seemed to still have a slight separation between what I was doing and what I was thinking/feeling. I would act impulsively (usually tending toward anger) and in the middle of it, instead of being strapped to the anger like a roller coaster, I realized my reaction was not justified in any way and realized I was triggered by something and I started thinking about what was actually bothering me.

It's a skill I still have to this day, and it's a lot easier to do while on Zoloft lol