How can I get long healthy hair?

I know the key to healthy hair is hair cuts

But the key to long hair is to grow it out and not cut it.

How can I do both?

I had really long hair which I loved, but it was unhealthy. I cut off 8 inches, (about 7 months ago) and started to cut it regularly every 6 weeks. The problem is, I go every 6 weeks and I feel like I just lose the hair I grew from the last 6 weeks. My hair is “boob length” and I want it to my waist, which is where it was before, but it looked like shit.

I just started using better hair products. I’m using miracle it’s a 10 shampoo and conditioner, their blow dryer protector (I only blow dry once or twice a week) and their deep conditioner

Any suggestions?