Pronouns must agree with themselves and maintain the same pronoun point of view throughout the sentence. In other words, don't suddenly switch from a "he" to a "you" or a "one" to a "they."
For example:
Incorrect
I dislike my job; you are overworked and underpaid.
When one travels to exotic lands, you should always take along mundane supplies such as bandaids, aspirin, and Kaopectate.
Correct
I dislike my job; I am overworked and underpaid.
When one travels to exotic lands, one should always....or When you travel to exotic lands, you should always....
