The reason the author of the Tanya appended the statement of the Mishna, ״A person must say, ‘The world was created for me,’” to the phrase “upon him in particular,” was so that the reader would not mistakenly think that it refers to him simply because he is a member of the Jewish people.
Rather, it is referring to him in particular, as an individual.
This is clear from the Mishna, because it states that a person is obliged to say, “The world was ereated for me,” as a conclusion to what was said earlier in the Mishna, where it is explained why Adam was created alone.
Just as Adam had no one to rely on and needed to act alone in all the worlds, so too every Jew should see himself as being alone.
Likewise, just as all the worlds depended on Adam’s divine service, which elevated them when he performed that service properly, so too each and every Jew has the same responsibility to serve God in a way that elevates all worlds.
Rabbi. Adin Steinsaltz