I have often regretted breaking something that has sentimental value or simply been annoyed that I have dropped a mug that was part of a set, but as I get older I shrug my shoulders and say that it simply isn't worth getting upset about as long as I have enjoyed the vase/mug/whatever for as long as I had it.
However, none of this compares to a broken Stradivarius!! I wince even thinking about it! And to think that someone has lent him another one!! (worth about 2.5 million pounds!)