The word "Shavuos" is a double meaning, it translates both as "Weeks" and "Vows". Chaza"l say that on Shavuos there was a double vow; 1) the Jewish people vowed never to leave G-d, and 2) G-d vowed never to leave the Jewish people.
We spoke last time about the power of vows in fighting the Yetzer Hara. On Shavuos night I was reading the Zohar of Parshas Yisro about the giving of the Torah, and I happened upon the following piece (in the third commandment, about not swearing falsely in the name of G-d) and here is a translation:
A vow to fulfill a commandment of his master, this is a truthful vow (like someone who swears truthfully in court), like it says "Ubishmo Tishave'ah - and in his name you shall swear". When the Yetzer Hara is prosecuting a man and enticing him to break a commandment of his master (and he vows to hold himself back), this is a vow that his master is praised through, and indeed a man must to swear in his master's name on this, and this is his master's praise. And Hakadosh Baruch Hu is praised through him. Like Boaz, as it is written "In the life of the Lord, lay here until the morning". Because the Yetzer Hara was enticing him, and he swore on this.
On Shavuos we read the story of Ruth and Boaz, and as we see in the Zohar above, when Ruth came to him at night, he swore in the name of G-d not to lay with her that night, and he told her to sleep until the morning. Even though Boaz was the greatest Tzaddik of that generation, he didn't trust himself without a vow.
Each person knows what they can / should make vows on, to protect themselves against the Yetzer Hara's enticings.
"Because of what you wrote, I decided to make a vow not to watch videos on youtube or similar sites anymore, for one year. I find that whenever I happen on those sites, even when I want to see something innocent, I am enticed by the countless improper videos that always pop-up and it's hard to hold myself back. Thank you for your great help!"