It may seem like a contradiction, but sometimes setting too specific of goals will bind you in and make achieving a target too difficult. Instead, setting a vague goal allows you the flexibility needed in order to achieve it.
For example, as a parent, finding time and energy to exercise is always tough. But in order for me to keep from gaining 10 pounds every year (I do love food & beer), I feel that exercise is important to my health.
I've tried setting goals like "run 3 times a week", but I never could stick with them. Some weeks I met it, but most were just too busy to hit the 3x mark. After a while, I'd gave up on the goal because I kept failing to reach it.
So last October, I changed my approach. Instead of setting a specific target, my goal was simply to run. Yes, I wanted to lose weight and get in better shape, but my focus was just to run. I knew that if I did, the chances of me losing weight increased and I'd probably end up being able to run farther than before. I also knew that if I didn't run one week, I could pick it right back up the next.
Now I'm able to run 4+ miles without dying. I haven't lost any weight and I've failed to run many, many times. It may have been an injury, a loss of free time, or simply a loss of motivation. It didn't matter though, because I stopped focusing on my past failures. I didn't care if I ran yesterday or not. I could run today.
I also stopped letting the possibility of future failures stop me. I quit worrying about not meeting my goal next week. I knew that if I ran today and failed tomorrow, that at least I ran once.
Sometimes you shouldn't invest too much in a goal. Just try it out. If it works, keep doing it. If not, no worries. Never assume you have to reach a specific goal for the journey to be worthwhile. There's value in every step you take.
Inspiration
A lot of the inspiration for changing my approach to running came from Zoe Gillenwater's 2013 CSSDevConf "Just One" keynote. Also, The Oatmeal has some great reasons to run.
This idea is very simple to Systems versus Goals. You can take all of this a little further and just stop setting goals.