Sometimes you are just plain lucky at the bridge table.
Consider this hand where you end up in 6(!)♠.
As small children may be reading this blog, I am not going to give you the auction other than that the opponents passed throughout. West leads the ♥K, standard leads and carding. Plan the play. You can safely assume that nobody else will bid the contract so an extra undertrick won’t matter.
Note added 2 February: Obviously, one of the ♣2’s must be the ♣3, but that hardly matters.
First, trumps must be 3-2 and even then, the trump loser will not go away. That means that you have to get rid of 2 heart losers. Ruffing both of them is impossible as this will create a second trump loser. The alternative is to set up the diamonds, with a 4-3 split in that suit, the fifth diamond can be used to discard a heart. That requires 3 ruffs and you just have enough entries for that. Obviously clubs have to split as well, but that is a detail. You should now be able to exactly plan the next tricks. If not, think about it a bit longer.
Done? Win the ♥A and start on diamonds. ♦A, ♦ ruff, back to the dummy with the ♠A, a second ♦ ruff with everybody following, back to the dummy with the ♠K (and hopefully everybody follows) and a third ♦ ruff. Assuming the suit splits 4-3, the 5th diamond will be good. An overruff at this point does not matter, as this will be the last trump anyway. Cross to a top club and cash the remaining diamond and play clubs. Whoever has the last trump, may ruff at some point but that is the last trick the opponents will get.
Guess what, it all worked out that way and, needless to say, we were the only pair in 6♠, for a good score.
On the next hand, we compensated for this overbidding by reaching only 2♣ on this layout
after a misunderstanding in the auction. That doesn’t look too promising as you expect the field to be in game. Wait until you see the east-west hands: ♠AJ with west, ♥QJ with east, ♦KJ with east, clubs 4-2 with west holding ♣Kx and east ♣Txxx. In 3NT, you start with 6 tricks and with the EW position as it is, it is impossible to find 9. However, 2♣ still made, for another good score when the field went off a few in the sensible contract of 3NT.
You have to time this over- and underbidding.