Unsuccessful lifters fail to track and monitor their progress. When something is important to people, they track it. Think income and expenses, blood pressure, and scholastic grades and you'll get the picture.
If you care about the results of your training, you simply must document and monitor not only your training, but also the results of those efforts. In other words, input and output, cause and effect.
A while back, while looking through my training records for clues about why my deadlift had stalled, I noticed a trend. During the weeks leading up to good deadlift performances, I'd been doing very heavy back extensions. And during periods leading up to crappy pulling sessions, I'd been doing zero back extensions.
My success had left clues, but I would have never noticed if I hadn't been keeping records.
Not keeping a training journal is the most obvious sign of a novice lifter. Don't be that guy. There are plenty of good tracking apps available, and rumor has it that notebooks and pens are still available.