Saddle fit is a critical component of riding horses. A saddle that doesn't fit can cause the horse or pony to be sore, which can lead to misbehaving, lack of desire to move, white spots, health issues, etc.
I like to compare an poorly fit saddle to a backpack. If you can imagine a backpack with a box in it, but the backpack doesn't fit right or doesn't have enough padding between your back and the box, then it pokes right through and causes discomfort. Fortunate for us, we can take the backpack off and readjust. Unfortunately for the horse or pony they either have to take the pain or act up to get our attention.
The link below will direct you to a website full of valuable information on saddle fit for both the horse, rider and the impact it can have on your overall ability as a horseman.