After almost 4 years of working out and almost 2 years of serious barbell training, I have only recently kept proper training records. When I say recently, it was precisely on 4 September 2011 that I started my training journal.
Some might feel like smacking me on the back of the head for not started it sooner. Much, much sooner. And some might think... "meh... I don't keep a journal but my memory serves me really well."
Yeah, so maybe you have a really good memory. But a journal does not only serve as a place to record your training. It also serves as a diary of sorts. Recording your training journey from being a weakling that could be mistaken for a fallen twig into someone with decent strength and a fairly attractive body.
And for me personally, it serves as a constant reminder of what I am really capable of. That I am NOT a weakling. That with a little push every training day, I will always be making progress.
I flip through my journal and all I see are improvements. If not in terms of the amount of weights lifted, it is in terms of the number of reps done. It amazes me how just a few weeks ago I was stuck lifting the same weights for the same number of reps day after day.
Now that I write everything down... I always have a target to hit each and every training day. And that will almost always guarantee progress.
If you haven't started a training journal yet, I strongly urge you to do so.
Apart from recording the type of workout, reps and sets... You could also record how you physically and mentally feel before, during, and after each workout. For example, I usually feel weak on my first work set but as I progress to more sets I feel stronger and stronger.
Therefore, I know that it is pretty much how my body works and not to feel intimidated by the bar when the first set doesn't go as well as I think it should.
And on days when training just sucks, I note down how I feel and what I ate (or didn't eat) and see if there is any clear pattern that contributes to an unproductive training day for me.
So yeah... Keep a training journal, folks. It requires very minimal investment and it is the best thing you could do to improve your training.