Yeah, duh, right? No one ever said running was easy. Even though we go for "easy runs" all the time. Sure, some runs are easier than others, and sometimes you hit a sweet spot where everything evens out and it feels easy for a while. But count on it, there will be times when running is just plain hard. Most of the time, really.
Hard part #1. Getting out there. Getting out of bed, getting away from work, making yourself run after work, no matter what time of day it is and what the weather conditions are, inertia is way easier than forcing yourself out the door.
Hard part #2. It hurts! Sluggish body, tired legs, getting moving is always a challenge.
Hard part #3. It's long! This is a kind of crazy mental thing. In my experience, no matter what distance you plan to run, it seems like a long way. Yes, nineteen miles is really long, but even six miles, even three miles seem like an interminable distance when you first start your run. That first mile or two? The longest miles ever.
Hard part #4. Speed is even harder. As much work as it is to go for a run at all, forcing your body out of its comfort zone hurts in a bigger way.
Now that I've done the negative Nancy thing, here is the upside of all these downers....
Better part #1. Once you actually put your clothes on and walk out the door, you are extremely likely to finish your run!
Better part #2. The initial pain does go away after you get going and warmed up. Really. It does.
Better part #3. Once you get halfway through your designated mileage, it gets easier because you have already finished more than you have left! Furthermore, even if the first couple miles seem to be really long, the further you go, the more quickly the miles will tick away. It's a strange truth. Even though you may be running at a slower pace, six miles out of a half marathon seem to pass much more smoothly than the six miles of a 10K. And in a marathon, the first 13.1 miles seem really easy. I think your brain strikes some kind of deal with your body to make this work.
Better part #4. The pain of running fast(er) some of the time makes a slower pace (whether in recovery intervals or separate runs) seem a lot easier! (And maybe your slower pace will become a little less slow...that's what I'm shooting for!)
And finally, even though running may sometimes seem hard for every minute you are doing it, the way you feel after you are finished is worth it all. At the very least, you have the sweet relief of stopping. And with some luck, you will also feel a glow of energy and well-being that will stick with you even after you've showered off the sweat and moved on to the rest of your day.