Answer: Desire (Hissaron) means that I simply want some fulfillment. For example, I am thirsty. Whereas an aspiration (Ishtokekut) depends on how much I really need it at a given moment, meaning how much I suffer now because I lack this fulfillment. This means that an aspiration is an addition to a desire and it measures the strength of the desire at a given moment, how much my ego is ready to suffer for the sake of reaching the desired goal.
In other words, how much are you ready to pay for this? Let’s see it now. You want to get it? No problem. How much can you give? We can measure your aspiration according to your answer. You say: “Well, a hundred.” “No, you should give a thousand.” “A thousand?” This is where you are tested with how much you are ready to pay. This is the way to measure your aspiration for the desired goal.
At the same time, a desire itself is simple. If something is free, I will take it. Obviously a person is evaluated according to his aspiration. A desire comes to us from the Creator, while we add aspiration through the environment. An aspiration is the fruit of our work, the result of our efforts.
From the 3rd part of the Daily Kabbalah Lesson 4/28/2011, Talmud Eser Sefirot