How to see that pleasure is not satisfactory?

Often, it is said that no external thing is satisfactory. It is said that all that is impermanent is unsatisfactory. But how can I see this? For example, I have some things I desire that I have never ever experienced. How can I be sure that they wouldn't grant me deep satisfaction once I have it, even if it is impermanent? Another example, what if little impermanent experiences bring satisfaction in an accumulative manner? Individually they fade, but there are more to come. Next to anatta and anicca, I feel that being able to see the ultimately unsatisfactory nature of conditioned phenomena would help with gaining a steady practice. However, doubt is in me.