Nursing is not the sure thing it once was. You cannot predict the future; you seem to think you will absolutely, positively land a job that guarantees 3 12 hour shifts, and these days that doesn't always happen. And, I'd suggest you shadow a busy nurse on a med surg floor for 12 hours so you have an understanding just how long 12 hours really is. You pull 3 of those in a row (with no lunch, holding your bladder and under the gun to finish charting with no OT) and you might reconsider.
I'm in Public Health Nursing and Case Management and work M-F, 9-5. I went this direction for many reasons, mostly because I tried floor nursing for 3 12's and saw waaaaay too many nurses burnt out, physically destroyed, unhappy, bitter and mistreated by money hungry hospital management. I ran the other way and have a desk job where my patient contact is minimal. I manage and coordinate care for post-op patients and arrange their treatment, working with them, their families, their docs, and all kinds of entities like medical equipment companies, home health agencies, specialists, etc. It pays well, I'm not lifting and running and holding my bladder, I help people, have a great team and cool boss. But it took me 4 years of BSN, and 6 years in the trenches to get here. It has not been easy, and now I'm also in full time school for my Master's because that's what nurses my age in this specialty are pretty much expected to do. So once again, full time work and no life, no free time, because that's how you stay competitive in any business.
Two things: the "majority of your life" WILL be spent at work, you better realize that RIGHT NOW. Unless you are born into money or win the lottery - sorry Charlie, you will spend most of your time working. That's life. 5 8s or 3 12s, doesn't matter. 30-50 hours a week of work is standard for most in the real world. And usually doing something you might be good at or like, but rarely something you truly love. That is the REALITY. Don't let the rainbow-pooping unicorns tell you different.
Also, remember you're not just gonna snap your fingers and have a 3 12s nursing job. Most companies are requiring BSN so let's see: you're 26. You get on a BSN program waiting list that's 1 to 3 years long. Then 4 years of hellish stress, and crushing debt after graduation. Then you will probably work in a nursing home or HH, where most new grads are only able to find work and get experience, for a year or two. Then MAYBE a hospital will hire you to a floor job. And because you'd be new, your schedule might be 4 12s and rotating weekends, or night shift every other night. You'll eat that misery for another year or two until you finally have enough experience and seniority to get that coveted 3 12s you seem to think all nurses just land after school. So you will be around 35 years old and already crispy around the edges, your back and feet shot, by the time you have the degree and experience to have what you dream of.
Sorry to bring the anvil of reality down on you so hard but someone had to say it. If you want to help people and have stable income, go into dentistry, or find another vocation and volunteer in your spare time. Unless what I described above is something you're able to commit to 100% and sounds like your dream come true.