I went through both.
My Quarter-life crisis happened after a few yrs of working, I did not like what I was doing. I started to look for jobs but could not find one in my area of interest. I was told I did not have the skills.
I studied further to upskill myself, took up pro bono consulting assignments, volunteered, took initiatives at work, learnt new skills, took up different roles. I was able to make a transition, it took me a few years to get to the role I wanted.
After working for 16 yrs my mid-career crisis happened. I was again not enjoying what I was doing. I did not know what to do next. My age, salary & past experience became a barrier in finding jobs.
I quit my job, upskilled myself by picking up consulting assignments, freelancing, learning hot skills, volunteering, doing internships with startups, becoming a co-founder, setting up my own startup.
It took me a few yrs to make the career transition again.
In both cases, it was a simple process of giving up what you have & learning new things.
A simple way to make a career transition is to make MICROSHIFTS (small changes frequently) to get to your destination.
Are you making micro shifts?
Where are you stuck?