Short sales fail for a variety of reasons, but number one on the list is poor or no communication from the lender causing the buyer to get frustrated and terminate the contract.
An inexperienced or inept listing agent will make the process more difficult. Be sure to assess the background of the listing agent and their dealings in short sales before signing a listing contract. Do your homework and make sure you account for the overall likelihood the sale will be approved by the lender.
Also, make sure you account for the deficiency judgement (shortfall in paying off your loan in full) and any potential tax ramifications as a result of the sale. All of these items can delay the process and likelihood of your deal closing in a timely manner or at all.
It goes without saying short sales are like the wild west of real estate and things can get messy. The best advice I can offer is to leave yourself plenty of time and, more importantly, to lower your expectations. Being realistic will minimize stress and make you less likely to make an emotional decision in the end. I have seen short sale transactions that have lasted over a year, so they aren’t for the faint of heart.