The bidding has passed round to me in 4th seat and I have 24HCP - open 2♦.  2♥ negative from partner, 2♠ from me (we cannot pass until game is reached so no rush).  So far so good.  Partner has 5♥ and correctly bids 3♥.  This is only promising 4 at this stage so the auction should carry on like this..... 3♠ by me showing extra length, 4♥ from partner, All pass and game bid and made for a joint top.  This is me however............  Instead of bidding 3♠ I bid 6♠ on my own and get doubled and go 3 down for 0%.   Lesson here, when you have a strong hand, partner is in control, listen to partner and make use of their hand.