You just keep doing it. I train very slow but steady. I think I've hit a bit of a plateau, but my functional strength is really noticeably improved - I can heave myself out of a swimming pool in one go, and can do about 2 full press ups in a row. I'm aiming for an unassisted chin up by the end of the year, although I'm not sure I'll make it. However, I'm enjoying training for it.
And the effect on everyday life is noticeable - I love being strong: I can easily get my suitcase up on the overhead rack on the train etc etc. That's the "functional fitness' gain - I've spent years as a cardio bunny but I'd never learnt about that. Getting into strength training in my late 50s has been a revelation.
My PB in a deadlift is 85kg. I'm currently training deadlifts in 5 x 4 reps at 70kg with a trainer, and at around 50kg on my own (I'm cautious!). The last set of 4 x 70kg was tough - I had to fully reset each time as I wasn't bending down far enough with my knees.
And my squat PB is 55kg - but that was 5 sets of 5, so I'm not sure what a 1 rep max would be. I'm 15kg squatting my bodyweight.
I was training last week with a pretty light weight - just 35kg on the bar, but my PT had me doing 10 sets of 10 reps each. So 100 squats (plus a warm up 10 with no weight on the bar - so just 20kg). It was tough but I didn't feel as exhausted as I thought I might, and I made sure the final set, I went as deep as possible (I can make the bar clang on the safety rails, as I'm pretty flexible in hips & ankles).
But that's 2 years of training ever so slowly (I'm in my 60s). I do one session per week with a trainer - he mixes it up a lot so I'm not always lifting (unfortunately) and about 2 bodypump classes a week which is light weights but I can pay attention to technique. Plus a mix of circuit class, Pilates, and some technical dance classes (jazz, ballet) most weeks.