The will chooses what is good. I like pizza, and the pleasure it gives me is good, so I can try and get pizza. Things that go beyond physical needs like friendship, can also be willed. Since I know friendship I can will it. When something is willed there is anticipation, and once it is attained there is joy. The greater the thing willed the greater the joy. For example, when we know that we are getting a pizza we are happy, when we get the best pizza we have ever had, we are even happier. So, since God is infinite and eternal when we love God and attain heaven we have infinite and eternal joy. The perfect satisfaction of the will is found in God