Being properly seated on your bike is largely a function of how the bicycle seat is positioned relative to the handlebars. If yours is a leisure type of bicycle it will likely have upward-oriented handlebars that require you to be in an upright position in the saddle. If your seat is leaning forward you’ll never be able to get comfortable. Likewise, if you have a high-performance bike with low semicircular handlebars and your seat is too low, too wide or strictly parallel to the ground your seat/handlebar relationship will be skewed and you’ll wind up in an uncomfortable and unsafe position.