Most of your expectations are as strong as when you know something. An example is when you drop a ball to the floor. You do not believe it will fall to the ground. You certainly expect it to fall to the ground. In fact you know that it is going to fall. There is no suggestion it will fall sideways of fly up into the air - your experience of the law of gravity tells you that is not possible.

Similarly, when you expect to be disappointed, you know we you be disappointed, because your past experiences dictates it and your inner knowledge tells you that this will be so. You will be familiar with the phrase "I knew I was going to be disappointed"...