Once upon a time there was a guy who had a big rock in the middle of his back yard. He didn't like it there because he kept hitting it with his lawnmower. So, one day, he decided to move it. He went out into his back yard and wrestled with that rock. He pushed, pulled, grunted, sweated, cussed, and pushed some more…but he couldn't budge it. Not even so much as one millimeter.
But this guy was determined, or stubborn, or whatever you want to call a guy who won't give up. He developed a habit of going out into his back yard and wrestling with that rock. He dedicated half an hour a day to fighting with it, although sometimes, maybe encouraged by thinking that he'd somehow budged it a little, he stayed out there longer. He was determined. Rain or shine, he went outside and struggled with that rock. He carefully developed strategies; if one way of pushing or pulling didn't work, he'd try another. He was going to show that rock who was the master.
Finally, after months of this, he still had failed to move that rock, even to get it to rock back and forth just a little. He gave up in despair, feeling like he had wasted his time, like he somehow wasn't good enough to move a rock.
But there were two things that this guy didn't realize: First, what he thought was a rock was actually the tip of a huge boulder sticking up out of the ground. More than 90% of it was underground. The whole rock was the size of a bus, and even the strongest man in the world couldn't have moved it. And second, although he considered that he had wasted his time, during those months of effort he had become the most physically fit guy in the neighborhood. He was much stronger and more muscular than he was before. But he hardly noticed this, because it happened gradually, and because he was trying to accomplish something entirely different—he was intent on a different outcome. Other people noticed it though; and he was healthier, and could do things more easily than before, regardless of whether he fully realized it.
The thing is, meditation can be like this. Don't be discouraged. Every effort we make has its effect.