The parsha begins with Yaakov sending messengers to his brother Eisav. "So says your brother Yaakov, 'I have dwelled with Lavan and was detained until now.'" Rashi tells us that Yaakov specifically chose the word "garti" (I have dwelled) for it has the numerical value of six hundred and thirteen. He was trying to convey a message that although he lived with Lavan for twenty years, he nevertheless guarded all six hundred and thirteen mitzvos of the Torah and was not influenced by Lavan's wayward behavior.
Rav Wolbe (Shiurei Chumash) says that we can gain another important insight from Yaakov's phraseology. Only because he felt that "garti" - that he was a ger, a sojourner in Lavan's house, did he succeed in keeping all the mitzvos. Despite the fact that he spent twenty years in Lavan's presence, he never became acclimated to his surroundings. He never allowed himself to be drawn into the culture or after the ideology of those living in Charan, because he always perceived himself as a sojourner and not a citizen.
One must be aware that there is truth to the claim that assimilation is a natural process. If a person perceives himself as a one of the populace "just like the rest of them," then there is nothing preventing him from becoming part and parcel of their culture and ultimately throwing off all vestiges of Judaism. Rav Wolbe related that when he was in Sweden, on the longest day of the summer the Swedes would dance around a tree and sing children's songs. Even though there doesn't seem to be anything intrinsically wrong with what they were doing, in reality there is a great danger involved. These songs and dances are an expression of the Swedish culture, and therefore, one must be extremely cautious lest he begin to acclimate to their way of life.
The most recent statistics show that forty percent of all Jews living in the Diaspora and fifty five percent of those living in America marry non-Jews. Unfortunately, assimilation has become "a natural process." In light of this fact, our avodah is to ensure that we maintain the correct perception of who we are. We are thankful to our host countries for allowing us to live there peacefully, but we are in no way part and parcel of their culture!