The first is that regret, like imagination generally, exists for a reason – this amazing cognitive ability is what allows us to plan for the future and, with luck, change things based on how we imagine they might turn out. Medallists who feel more regret may well go on to train harder, and smarter, and so be better able to win gold at the next Olympics. Regret, like so many of the territories of the mind, can hurt. It hurts whether we can change how things have worked out, or not, but the feeling is built into our brains for a good reason (however little comfort that provides).
The second thought that might help us deal with regret is to realise that there are many possible worlds we could compare events to. It's natural for many silver medallists to feel that they've missed out on gold, and to the extent we can choose what we compare ourselves to, we can choose how we feel about our regrets. We can use them to drive us to future success, but also to appreciate what we do have.
So maybe it isn't all bad for Blake, Maroney or Seebohm after all?