The surface pressure is related to the isobars and high vs. low pressure systems. The barometric pressure will have an effect on the stability of the day. High pressure days are generally more stable and usually sunny but may also result in sharper thermal edges. Low pressure days are less stable and may have cumulous clouds and tend to have smoother edged thermals. High pressure systems descend in a clockwise rotation. Low pressure systems ascend counter-clockwise. The barometric pressure trend will help you determine whether a weather system is arriving, leaving, or sitting over you.
The barometric pressure for a day is not a “deal breaker” for flying. It is merely another data point which will help you determine what the day will be like. The standardized pressure is 29.92. If you note that it is at 30.10 you can expect sharper thermals.