Rav Tzaddok HaKohen brings us a fascinating idea and its proof this week. This is it: Avraham Avinu was a man of chesed, right? Correct - Chazal tell us this on plenty of occasions, and it is hinted to in the Torah text too. But there is only one place where his chesed is mentioned explicitely. That's the start of this week's sedra, where he gives food to the three passerby people. There's only one problem. These were not people, they were angels, and so did not need any food. What emerges is that the only time the Torah chooses to explicitly mention Avraham's chesed is when he thought he was doing chesed but he wasn't really [coz angels need no food, etc]! Why not mention the many other 100% acts of chesed Avraham did, and why (instead) mention this one with the angels?
Rav Tzaddok answers that it is to teach us a fundamental principle, which needs much delving into and proper understanding, and it is a shame to write it so briefly like I'm doing now. He basically says that our free will is housed in our 'ratzon;' what we want. He is of the opinion that we do not realy have free will over our actions; our free will is over what we WANT to do. We might genuinely want to do a mitzvah, but HaShem may prevent it from being carried out, and we still get reward for the thought - as long as we actually wanted to carry it out. Here, with Avraham avinu the Torah specifically picks a case where he thought and wanted to do a mitzvah of chesed, but it was not really an act of chesed, to teach us this lesson.
THE MORAL: WANT AND DO AS MANY MITZVOS AS POSSIBLE!