I got injured last year doing a CrossFit workout. All of a sudden during a clean and jerk my right knee buckled, and started to hurt a lot. Luckily I didn't need surgery, but it's amazing how derailed I became in terms of exercise. Long story short I ended up spending a few months doing physical therapy, and then never got back into an exercise routine.
I let this injury snowball into a million reasons why I couldn't workout. At first I was doing physical therapy, so convinced myself that this was sufficient (hint: it wasn't). Then after I finished physical therapy, I knew I couldn't ramp right back up to an intense workout like CrossFit, but didn't quite know how to structure my own workouts. I spent a few months figuring out how I would work out on my own (thanks NerdFitness!), only to then ponder endlessly about when exactly I would actual conduct my workouts. The last few weeks were spent figuring out which gym I'd go to, how I would secure my belongings while I worked out, and how I'd shower and change clothes after I was done. Clearly I let my pensive nature get the better of me, and as a result didn't actually exercise.
But today I just went and worked out. Although every step of the process was awkward (leaving work, the locker room in general, being around 'gym bros', etc etc) it was totally worth it.
Every time I form (or in this case, reform) a habit, I find taking the first step is the hardest. Now that I've done one workout, it's just too easy to repeat this over and over and over. Within a few months it will be like second nature, and I'll be substantially healthier.
It's days like today that remind me that I need to live more like Nike's motto, and Just Do It.