There's a lot involved in good training... but the most important thing is to simply get out there and do it. We sometimes say that "only perfect practice makes perfect" and it's easy to make the leap from that to "if I can't train perfectly, I shouldn't train." Nothing could be further from the truth!
We all have days that our energy isn't there or stuff distracts us and the monkeys rule the brain. Those are sometimes the most important days to train! Do something... Force yourself to do a drill, review a form, practice your stance... DO SOMETHING! Why? First, training often fixes those issues for you... Second, reality doesn't give us warning and time to be psyched up and ready. Learning to work through those periods in training gives you the tools to work through them in reality. Finally, repetitions count... "Perfect training" is training done properly, with the right technique and principles... not being in a perfect mood or mindset.