I think the translation is close, but may be slightly off (please check my math here, Im not an expert!):
Loshas zhoroon anni[(watch over / look after) heart-mine(inalienable possession) mine]
^^Because the heart is part of the body the "oon" attachment is sufficient. Adding "anni" for "my" would be redundant.
haji anha vannevak mae ma yeroon.[(because of) I (will leave something {future tense}) it with (you+ from-you indication)]
^^haji may work here, but seems unneccessary. "k'athtihari" might be nice - meaning "it seems"
^^annavalat (the verb for leaving something) is conjugated for future tense here (addition of 'v'). past tense would be 'annava' I believe, though 'azh' meaning 'I gave' might work better.
^^mae means "his/hers/its" instead of "it". The pronoun you want here is 'jin' I believe, referring to something that is close to the speaker, as opposed to using 'haz' or 'rek'.
^^the 'oon' added to 'yer' indicates possession or direction, in this case 'from you' ('aan' would be to/for you). I think it can be dropped here. Unless Im mistaken this is in the accusative case, so 'yera' would be the appropriate form.
So my proposed change would be:
Loshas zhoroon, k'athtihari anha azh jin ma yera.If the above seems off please post and let me know