And I often have the same question: do I need to find that core wound?
Well, I think that identifying your
core wound is helpful, although it's not necessary to do this with a lot of words. Whether you heal this wound in an instant realization or during a long and extended process is just up to you and your current personality. Both ways can work just as fine.
I agree with
@John Tat that these problems are not really the problems of our Souls but that each time we come back to a new life, we somehow pick up the energetical backpack that we left behind the last time we died. Don't ask me how this all works but after reading and hearing so many personal stories about reincarnation, I came to this conclusion. It also makes sense from a broader perspective. So probably this is exactly what some people refer to when they use the word karma. And probably ego as well. A lot of traits that are called 'ego' are just inherited believes from past lives. (for example, a dominant person might act this way to compensate for the feelings of insecurity and fear of abandonment, originated from situations in former lives). Maybe ego and karma are very much the same things.
I'll clarify this with my personal experiences and personal theory. One of my core wounds is
abandonment. This seems to originate in my past life as a Maya girl. I sort of feel that I had already cleaned op my spiritual backpack before that life and somehow I decided to start a new cycle of lives. In that life, first I lived in perfect harmony and pure happiness as a little girl. Then I was pushed out of this Paradise by family/culture/circumstances and was taken to another place and ended up being killed. This had caused me such a soul shock, that somehow in the lives afterward I replayed a lot of details from this causal life over and over again. Several times I died at the same age: around 14 years old. Several times I experienced ending up alone in a hostile environment. Several times I experienced a perfect childhood, until a great break. Sometimes I choose to be alone, just not trusting human bonds.
In this life, I don't have abandonment issues but I think my strong ego solved that 'problem'. My ego expresses herself by a compulsive need to be independent of others. If you don't need them, you can't be abandoned, seems to be the drive.

(Spoiler: it doesn't work that way)
Back to the initial questions about resolving old pains, wounds and how fast they might heal.
I've experienced
instant healing, without even seeking it. It happened when I had witnessed my young son's regression to a former life as a boy soldier (sniper) and his death on the battlefield. I had been sitting in the corner of the room without interference. Just until one moment, when I rose up and asked him who had been his mother in that particular life. And while we were just smiling and laughing at each other, I felt these weird energetical waves going through my spine and body...
From that moment on, I no longer experienced panic attacks about losing him to the military anymore. This experience is a cherished miracle to me.
I also experienced
long-lasting healing over a period of weeks and months. On these occasions, rages of fire went through my body, over and over again. Reliving anger, abandonment, and shock. This happened after I started to remember the execution of my former husband in Prague and also when I started to remember my life and death as a Mayan girl. On both occasions, I just let it happen until it all faded away into acceptance and calmness.
Wow, while I am writing this, I just remember another example of instant healing without much context. Last winter, I had to cross a dark wood early in the morning on my way to my work. I went by bicycle along a small path, Without moonlight or lantern, there was total darkness. I didn't care about that because I am not afraid of darkness. Then, first slightly, I started to get the feeling someone would hit me on the back of my head. These feelings grew stronger by the day. I started to imagine a black carriage, horses, feelings of an ambush.
I still was not afraid of anything happening to me on my way to work, it was just that these feelings of getting hit very hard on the back of my head grew too strong, made me feel too uncomfortable. When I arrived at my work one morning, I somehow had a minor accident by my own clumsiness and I got hit very hard on the left side of my head. It hurt much but I was also in surprise that 'it finally had happened'. From then on, I never experienced those feelings anymore while crossing that wood in darkness.
Seemingly this blow on my head had released an old energy/memory to be freed and dissolved without knowing what exactly had happened in the past.
I think to let go of the past might happen by just releasing the block of frozen energy in your system (even without much context) or by going through a process that leads to acceptance and peace.