Whenever a person anticipates an event they count down to it, 49 days left, 48 days left, etc. Why by sefiras haomer when we are counting to matan torah do we count up 1,2,3,...?
R' Pincus explains as follows. In Parshas Vayetze the Torah describes Yaakov's wait for Rachel as follows "ויהיו בעיניו כימים אחדים באהבתו אותה", they were like a few days because of his love of Rachel. If you ask anyone they will tell you just the opposite. When you are anticipating something that you want every day that you have to wait is torture. So why did the days go by quickly for Yaakov? R' Aharon Kotler explains as follows. Take 2 men A and B, A is promised $1,000,000 in 100 days while B is promised that he will have the opportunity over the next 100 days to make $10,000 a day. A will regard every day as an obstacle keeping him from his money and would like to skip over them. Therefore, each day is like torture. B on the other hand will cherish each day, each day needs to be utilized to it's fullest to make the $10,000. For him the days are meaningful and full and therefore pass by quickly. Yaakov was like B. He understood that he needed to utilize those 7 years to build himself up, to perfect hic character and his torah knowledge so that he could father the 12 shevatim. Therefore, for him, the 7 years were meaningful and full and therefore they passed by quickly.
The same concept can explain why we count up. The days of sefira are supposed to be days of growth where we prepare to receive the Torah. Just like B would count up, on day 1 he would say so far I have made $10,000, on day 2, $20,000, etc. we also count up to show that each day is valuable and that we are utilizing each day to it's fullest. Counting down on the other hand, shows that you don't value the days you just want them to pass, they are meaningless.
This is a great lesson for the days of sefira. We are not just counting down to matan torah. These are not just empty days. Rather we are supposed to be counting up, building oursleves up and preparing for matan torah by increasing our limud hatorah and kiyum hamitzvos.