R' Tzadok Hacohen of Lublin explains (in the beginning of "Machshivos charutz") the deepest secrets of the battle with our evil inclination. He explains that there are two paths in fighting the Yetzer Hara, and that they are both legitimate only when used together, i.e. although some people have more of a connection to one way and some to the other, neither one is enough by itself.
One way, is the way of Yoseph Hatzadik, whose concentration was on constantly building himself up to be an "Adam Hashalem". He therefore concentrated very much on building up his self-control.
The other way is the way of Malchus Yehudah, where the concentration is totally on living with Hashem and relying on Him to save us from the Yetzer.
(Chazal say that the way of Yoseph is more dangerous because if you c'v fall, you can loose everything. R' Shimshon Pinkus Zt"l used to talk about this a lot. He kept on saying that what's going to bring the geulah is the "Yehudah way" and he brought many proofs to this.)
R' Tzadok explains that the holy sons of Yaakov Avinu had a very small imperfection. While Yoseph excelled in his way and everyone else excelled in Yehuda's way, each side felt that the other way is a contradiction to his way: How can I fully rely on Hashem, if I am working on my self-control? The shevatim felt that such a focus on self-improvement and self-control is a complete contradiction to their way of bitachon in Hashem!
This - he says - was the root cause of "Michiras Yoseph".
It was also the reason that Klal Yisroel did not fully accept the Torah willingly by Har-Sinai. They had experienced "Yetzias Mitzrayim", which was the greatest manifestation of the Yehudah way. The Jews in Egypt had fallen extremely low and they were so desperately dependent on Hashem, that Hashem broke all the laws of nature for them. At the time of Kabbalas HaTorah, the last thing they wanted was to build themselves up to be a Mamleches Kohanim (a Kingdom of Priests), because that would seem to make them less dependent on Hashem and then they wouldn't be eligible for such Divine intervention.
R' Tzadok goes on to explain that when the Meraglim gave their report about how great and fearful the giants of Eretz Yisroel were, the Jews said: How in the world can we be expected to fight forces that are so much greater than us? "Let us return to Egypt" - let us go back to being totally powerless and desperate, and have Hashem fight our battles!
So the obvious question is: Didn't they have a mighty good point?
The answer is - says R' Tzadok- that if you understand Hashem himself is the heart of Klal Yisrael, then the question doesn't start. Yes of-course we need Hashem, BUT HE'S RIGHT THERE INSIDE OF US! Yes we need to take responsibility, yes we need to build up our self-control, yes we need to turn ourselves in to holier and holier people, yes we need to fight our own battles, but all this is done only through the power of Hashem.
By the great miracle of Purim, Klal Yisroel were finally able to grasp this, and that is why we willingly accepted the Torah completely. This was because we saw that we don't need "Yetzias Mitzrayim" style miracles - we don't need Hashem to break the laws of nature. (In-fact it was all only meant to be a one time occurrence.) We don't need Hashem to "take over". We don't need it because Hashem is with us always, within nature. We don't need to be powerless and passive, we just need to tap in to our inner core. When we realize that everything we do is only with the power that Hashem is constantly giving us, then there is no limit to our power.