Originally Posted by
rubikfans
Were you the sender or the receiver?
One method I found worked well for me is to generate a transaction with the unconfirmed output of the transaction with a very high fee.
That will favour your second transaction to be included in a block. In turn, including the first transaction as well.
Another method is to attempt to cancel the transaction by double spending one of the input with a much higher fee. If the double spent transaction gets included into a block first then the earlier transaction will be invalidated, canceling the transaction. However, this may require a more flexible wallet since most wallet prevents this.