Patience is a virtue, and rewards those who practice it. Impatience has the potential for lack of progress or even regression.
For many years, I was impatient when it came to training. I had 10 goals on my plate and attacked each of them with equal vigor in hopes they would be achieved in the matter of a few months or a year—tops. Part of this was self-experimentation, me wanting to find out of my body responded well to this or that method, if I could really handle all of that volume and intensity. The other part was ignorance. For those at least moderately familiar with strength training (and other types), you'll understand that "quick" doesn't exists in regards to improvement. It's a slow, arduous process that actually isn't terribly complicated during the initial stages: training fairly intense fairly often, recovering well, and being consistent virtually guarantees improvement. However, without one of these three tenets, the stool topples over.
Patience can also be looked at from a "satisfied" perspective. At what level will you be satisfied with your fitness? For some, it's never (a discussion for another post), and for others, it's at 5 rep back squat with two times their bodyweight loaded on the bar.
After identifying these satisfactory goals, the time it takes to get there can be calculated. For example, take the 2xBW, or 315 lb, back squat. Let's say someone can currently squat 225 lb for 5 reps. 90 lb is then needed, which plenty of people can achieve in 1-3 years. So why are you rushing and risking injury or burnout? Take it slow, enjoy the process, and reap the benefits when they arrive.
To those out there trying to game the system by only doing HIIT-type training to prepare for a marathon, newflash: there's no such thing as a free lunch.