The idiom "on the crest of a wave" means to be at the peak or high point of success, popularity, or fame. It refers to being at the top of one's game and riding the momentum of success.

The idiom "sealed with a kiss" means to complete or finalize something. It is commonly used when two people exchange a kiss after getting married, indicating that they are now legally bound together and the marriage has been sealed.

The idiom "go to the dogs" means to let things deteriorate or to go into decline. It can also mean to be willing to do whatever it takes to achieve a goal, even if it means taking risks or making sacrifices.

The idiom "to a T" means to do something exactly as it should be done or to describe something accurately, completely, and in all details. It is often used to show approval or admiration for someone who has performed their task to perfection.

The idiom "sleep tight" is used to wish someone a good night's sleep. It implies that the person will have a restful and peaceful night, without any disturbances or worries. The phrase can also be used to express confidence in someone's ability to stay safe during the night.