This is an interesting topic, and no doubt there's a literature on it,
but I don't know it, so no references. Sorry.
Reflexives, like any set of pronouns, have multiple uses. Plus not all languages have them.
In English, the general rule is that,
- when there are two coreferential NPs in the same clause,
- the second NP is required to be a reflexive pronoun.
Exceptions abound, as noted.
Let me just remark on the presenting examples below:
(in all of these, we are presupposing that identical pronouns refer to identical people, OK?)
First, there's the ones that don't allow reflexives, but require personal pronouns:
- You bring something with you/**yourself.*
- You have something on you/**yourself.*
- You pressed her to you/**yourself.*
Then there's the ones that swing the other way -- they require reflexives and forbid others:
- You draw attention to **you/yourself.*
- You can try it out for **you/yourself.*
- He killed **him/himself.*
Finally, there's some that can swing both ways; both types are OK:
- You have something in you/yourself.
shipr has pointed out, the second pronoun in the first bunch refers to your (or his) body,
not to the subject you (or he), which refers in each case to the person's identity/soul/mind/spirit/character/personality/
insert metaphor here,
and not to the body specifically This means it can be considered as not coreferential.
Hence the rule does not apply.
As for whether you have something in you, or whether you have something in yourself, one assumes first of all that the something in question is not physical. If for instance it's a defibrillator installed in your chest, then the reflexive would be ungrammatical. So it must be spiritual/mental/emotional/judgmental/abstract/
insert metaphoric adjective here.
But I can't go much farther than that.
It's an exception, and there may be others, if you look for them.
Or literature. Ross has a paper on "Clause-Matiness", which looks at it, I think.