The quantity of the sample size has a significant influence on the standard error. Since n is the denominator of the standard error formula, as n increases, the standard error increases. The more data that you have, the more accurate you can be.
Lets say you work at UPS and you're on a delivery schedule. You have a mean delivery time of 3.50 days with a standard deviation of 1.2 days and 100 is the sample size. 0.12 days would be your standard error. If we were to increase that sample size to 225 the standard error is 0.08 days. The standard error went down because of the increase in sample size.