The Parsha begins with Yaakov sending a message to his brother Eisav, "So says your servant Yaakov, I lived with Lavan and was detained until now" (Bereishis 32, 5). Rashi writes that the word 'garti'- I lived, has the numerical value of six hundred and thirteen. He was implying that although he lived with Lavan, nevertheless, he kept all six hundred and thirteen mitzvos and did not learn from Lavan's evil ways.
Rav Wolbe (Shiurei Chumash) explains that it was only because Yaakov felt like a sojourner - 'garti', did he succeed in keeping all the mitzvos of the Torah. Those living in Charan definitely had their own culture and all the residents living there grew up absorbing their ideology. Nevertheless, even after twenty years, Yaakov perceived himself as merely a guest, since he did not acclimate to his surroundings in the slightest. It was only because he stuck steadfastly to his roots that he succeeded in not being influenced negatively.
The Mashgiach adds that there is some truth to the claim that assimilation is a natural process. If one behaves as the gentiles around him, this will automatically lead to assimilation. He related that during and after World War II, he resided in Sweden for eight years and he beheld a number of their customs. On the twentieth of December they would dance around a roasted pig. Additionally, on the longest day of the summer, the entire populace, men, women and children, would dance around a big tree and sing children's songs. Even if there is nothing intrinsically wrong with what they were doing, there is great danger involved, and someone endowed with a heightened sensitivity can perceive how joining in such customs distances a person from the Torah.