One thing I'd like to add is that if you've mostly been doing the same workout for 3 years, you need to switch it up. Not just implementing different machines/motions, but changing your overall routine. If you've been doing a day split, try mixing that up for a month. If you've been working a certain rep range, try hitting your body with a lower or higher rep range for a brief while (2-4 or 12-15 instead of 6-10). If you've been doing 80% the same workout for 3 years, your body will take much more to progress at any speed.
Also most of us take a scheduled rest period every once in a while. Life usually plans these for me, but if you're very regular, then taking a week and just doing moderate cardio wouldn't be bad every 3 months or so.
Some specific 'proven' workouts around here might not be a bad idea to mess with to switch it up, just make sure to not think you've found 'the one' and never change from that either. To make your body adapt, you must adapt.
Perfection in motion. BS CPT - NPTI NASM
"We must not forget that even in the most perverted and cruel human being, as long as he is human, a small grain of love and compassion exists that will make him, one day, a Buddha." -Dalai Lama