Rent or Sell? Rent wont cover all costs

We live in a mid-town Manhattan 1 bedroom (790 sq ft) The principle on the mortgage is: 973 /mo The interest on the mortgage is: 1082 / mo Fees, Taxes, insurance, misc cost avg: $1992 /mo So a total of about $4046 / mo It will rent for $3100 a month. That will cover the interest payment and all fees but won't cover the principle. Is it worth keeping - hoping it will appreciate in value in the coming years? or should we sell it. We will probably incur a loss as we would need to pay the agent fees + lawyers costs etc. In our building we can sublet out with an additional fee. That is included in the $1992 amount.