A number of events (and pitfalls) can occur between the time you sign your contract to sell and the final closing. There is no way to guarantee that your journey will be a smooth one, but at least do your part to make everything easier.
One item you have no control over is the bank's appraisal of the property. The lender needs to know that your home has sufficient value to cover the amount of the loan. A lender usually will not lend more than 75% to 80% of the value of the property (this can be higher, depending upon the lender and the buyer's credit rating). Although you do not have control over this event (the lender automatically sends an independent appraiser to tour the premises), it should not be a problem for you, as long as the price reflects the home's true value. It may cause trouble for you if the buyer is trying to buy more home than he or she can afford. Hopefully, the selling agent has pre-qualified your buyer.