Intensity in training has its place. In fact, it's an absolute requirement of effective training, especially as you become more experienced. Problems arise, however, when people allow intensity to interfere with consistency.
Much like proper nutrition, smart training is best viewed from the 40,000 foot perspective. Imagine if someone said to you, "Dude, last Tuesday I ate perfectly. No processed foods at all, I hit my macros and my meal timing was perfect. I was 100 percent dialed in!" To which you'd probably think, okay cool, but what about the rest of the week? Why so much emphasis on a single day?
Training is like that too. No single workout, no matter how hard you crushed it, is all that meaningful. Instead, what matters is your average intensity over long time periods, not how hard a single workout might have been.
Whenever an athlete tells me he's on the way to the gym but he's super tired, I always remind him that even a half-assed workout is far superior to a skipped workout. It's the difference between making slight progress and backsliding.
It's critical to set realistic goals at the outset. T Nation contributor Bret Contreras often says, "Out of every three workouts, one is fantastic, another is just 'meh', and the third totally blows." This is especially true as you become more and more experienced.
Job number one is consistency, regardless of whether you like to train three days a week, four days a week, or whatever. Your job is to hit those numbers without fail. Then work as hard as you can within that foundational framework.
But What If I Have To Miss a Workout?
If missing a workout is simply unavoidable (and it sometimes is), just combine the missed workout with the next scheduled session, but with only half of the planned work sets. While not ideal, this strategy is a fantastic damage control tactic when life gets in the way of training.