sometimes its like a revolving door

No sooner had I taken on a new member of staff to cover a few hours a week in the shop than she turned round and revealed that she had accepted a full time job elsewhere. I suppose I shouldn't get too upset; in the current climate everyone wants to earn the maximum amount they can, I suppose and I couldn't offer her any more hours but its quite frustrating to go through all the hassle of recruiting for them to work a grand total of 12 hours before handing in their notice