I'll admit it. Once I drove into a crowded gym parking lot only to turn around and go right back home. My excuse? "It was too busy there to work out". I told myself I'd try again tomorrow at a different time and do twice as much (that probably didn't happen). Lame, I know.
It takes more energy to come up with the perfect excuse than it would to actually exercise. Think about it. You have to come up with something creative. You're too tired. Wednesdays are weird. You missed the cat. That sounds so much better than "I don't feel like it".
Next comes the internal struggle to convince yourself it's justified. At first it's an even battle. Half your brain thinks it sounds like a valid reason. The other half knows it's complete B.S. Slowly but surely the latter half loses and you've persuaded yourself to skip the work out.
The worst part happens next. Even though your decision was sound at the time, your B.S. detector just won't shut off. The guilt sets in. It's too late to go back and change things but you can't stop thinking about it. You feel sluggish and miss that sense of accomplishment you get after a good workout. The next day everything you eat reminds you of those extra calories you would've burned the day before. You'll work extra hard at the gym today. However, the additional pressure only makes another excuse look more appealing.
Looking back, the decision to skip that workout weighed on you for over 24 hours. It took some time to come up with the excuse, to justify it to yourself and others, and to then deal with the amplified guilt. If you just cut the crap and went to the gym, it would've only consumed an hour of your day.
The hardest part of exercising is making the choice to do it. No one ever ends a workout in a bad mood wishing they hadn't done it in the first place. Pick the endorphins over the excuses. Turn off your mind and let the autopilot setting guide you.