In conjunction with the covenant that Bnei Yisroel would make with Hashem to perform the commandments of the Torah, Moshe tells Bnei Yisroel the following: "Haskeis U'shema Yisroel, today you have become a nation to Hashem your G-d and you shall heed the voice of Hashem" (Devarim 27, 9-10). The Sforno explains, "'Haskeis' - picture in your mind, 'U'shema' - and contemplate, 'And you shall heed the voice of Hashem' - when you picture this and understand it, then you will undoubtedly heed the voice of Hashem."
Rav Wolbe (Alei Shur vol. II pg. 274) writes that according to the Sforno the Torah is revealing to us that picturing Torah concepts can aid us in our fulfillment of the mitzvos. For example, we are commanded on Pesach to perceive ourselves as if we left Egypt. This includes conjuring up a picture of this momentous occasion. We should imagine the pillar of fire that illuminated the area, the awesome procession lead by Moshe and Aharon - each family surrounded by ninety donkeys laden with bounty - all marching out of Mitzrayim in an incredible display of Hashem's might. The same concept applies to the commandment not to forget the revelation at Har Sinai.
Picturing these events that defied all the laws of nature is not merely a fulfillment of a specific mitzvah; it is an essential part of our emunah. One's emunah in Yetzias Mitzrayim and his belief that the Torah came from Hashem, is not complete until he has depicted and contemplated these occurrences in his mind. Conjuring up a picture gives life to these events of the past, and this simulated experience can make an indelible impression on a person's life.
This is an activity that can be performed anytime and anywhere. Picture the Bais Hamikdosh, Akeidas Yitzchok, Yetzias Mitzrayim, Har Sinai, or any of the numerous momentous occasions in our rich history. Take a few minutes to let your imagination draw as many details as possible. The more time invested, the more real the event becomes. This is a simple exercise than can not only strengthen one's emunah, but hopefully aid one's preparation for Rosh Hashana. A true "picture" of Hashem as The King over the entire world will make it easier to accept the yoke of Hashem upon himself.