title_body: What decides where is the break between syllables?
upvoted_answer: I think as a general rule, a syllable comprises some combination of the following kinds of one or more of the sound types of your language:  vowel, liquid, consonant.  
  
  You've decided on (C)CV.  And if there are two C then one must be a sibilant and the sibilant must follow a stop. So you can have syllables like sa, ta, tsa  but apparently not sta.  You might then have a words like tasa &amp; satsa &amp; tsatsa.
  
  In English, we'd probably break that into SAT-SA.  Your language will likely differ, because everyone knows that a syllable can't end with a consonant!  So, they'd much more likely break the word thus: SA-TSA!
  
  I would argue that what little you've described of your language and its rules speaks in favour of E-PSE rather than EP-SE.  The only thing you "did wrong" was to apply the English rule rather than the rules that apply to your invented language! The second thing you did wrong was to second guess yourself based on the English rule!