What is wrong with this sentence?
The following sentence does not look or sound right to me, but I can't pinpoint the problem and don't know how to make it better.
If someone is causing you stress, you need skills to handle both them and you
Grammatical experts, please help. Any suggestions for improvement?
There are two things which might be niggling you.
The first is the mismatch of singular and plural which Gill mentioned. (As a side note in relation to Micha's comment, in the old days the masculine pronoun was inclusively to encompass female 'someones' as well, but modern sensibilities do not allow that, so the grammatical mismatch is now much more acceptable. Even if grammatical sticklers like me don't like it.)
The other possible cause of concern is a wonderful thing called zeugma. Using the same verb in one sentence with two different meanings. So, handling someone who is causing you stress actually means something different from handling yourself - how you interact with someone as opposed to how you control feelings.
The classic example of this is in a song called 'Have some madeira, m'dear' by Swann and Flanders. '..he put out the the cat, the wine, his cigar and the lamps'. Works well in comedy, less well for serious writing. Steve, you picked it up subconsciously in your rewording.
Micha Wotton Head of Development at SavvySME
While not strictly correct, using 'them' in the singular sense is acceptable (and in common use) since there is no other non-gender-specific third-person singular reference, and alternatives are more awkward. In this case the singular 'someone' is enough context to understand that 'them' is also singular. Other examples might be "If someone calls for me, tell them I'll call back" or "If you see someone struggling to carry a load, give them a hand".