Maybe you were too heavy-handed with the salt or perhaps you didn't take into account other naturally salty ingredients. Whatever the case, if the sauce you made to accompany your meal is way too salty to be served, don't throw the whole batch out. That would be a waste of money. You can fix the problem by using everyday staple food items that you likely already have on hand that will mask the saltiness or absorb it altogether.
Add lemon juice, a few squeezes at a time. The acidic qualities in lemon juice can mask some of the salt flavor if it is not too salty, but you must taste as you add the lemon juice so that you don't end up with sauce that tastes too lemony.
Drop a peeled potato into the sauce and cook for about 20 minutes. Potatoes are like sponges and will absorb much of the salt in your sauce. It will also absorb some of the liquid, so you can add more liquid to the sauce to further dilute the saltiness.
Double the batch of sauce. If you just double all the ingredients for the sauce except for salt, you will effectively dilute the saltiness. You may have more sauce than you need, but you can freeze the rest for another time.
If you have a particularly large batch of sauce, you may want to use more than one potato to absorb excess salt. If you don't have a potato on hand, try using a few slices of bread to absorb the salt.