As we mentioned earlier, it's much easier to get excited about fulfilling positive mitzvos than to refrain from violating a negative commandment. We feel so much more accomplished when we perform a good deed - e.g., davening with kavannah, or learning with a geshmak - than we do when we merely refrain from doing what is wrong.
But feelings can be deceiving.
In 1967, for example, Neil Armstrong, the first man to step on the Moon, was celebrated as a national hero. While he certainly was brave, why was he the hero? Perhaps the scientists and technicians who developed and constructed the spaceship should have been celebrated. After all, it was their intellect and hard work that made the entire project possible; Armstrong basically followed instructions. The answer is, of course, that he did the spectacular. The image of Man walking the surface of the Moon was dazzling - and Armstrong was the man who made that image a reality.
The lesson? We get caught up in our feelings and confuse the spectacular, that which we can see and feel, with actual worth.
The fulfillment of an asei may feel more holy, but the Gra tells us that in fact, we are granted much more reward for refraining from sin.
The Mishnah teaches that Hashem grants each and every tzaddik 310 "worlds" of reward. The Gaon writes that a full 300 of these "worlds" are granted to the tzaddik because he turns away from evil (sur mei'ra), whereas only 10 worlds are given to him because of his good deeds (asei tov). What a contrast! 300 "worlds" for refraining from sinning compared to just 10 for actively performing mitzvos.
This emerges from the Gra: It may be easier to appreciate the performance of a commandment - celebrating Yom Tov, learning an intriguing "daf," or praying a meaningful tefillah - than to refrain from transgressing. The feeling of spirituality, the "wow factor," is indeed more readily accessible in the cases of "asei tov." But the substance of a Jew, the foundation upon which it is all built, is the "sur mei'ra."
When we commit to be more careful with what we see, we are laying that foundation, and we are therefore rewarded with the bulk of our reward in Olam Haba, the "300 worlds" earned through "sur mei'ra."