Unfortunately, there is no expression in English that is quite like 舍不得你. Greg's suggestions are good. Some other options: "We'll miss you." "We hate to see you leave." "We're sorry to see you go." "We've enjoyed having you here." "It's been great working with you."
"Take care" is like 保重 . "Best of luck to you." "We wish you well."
(I used "we" in my examples, since the person is leaving a company, but of course you can also say "I," if you want to be more personal.)