The idiom "black mood" refers to a state of sadness, depression or melancholy. It is often used to describe someone who is feeling down, upset, or out of sorts.

The idiom "dig one’s own grave" means to make a mistake or error that leads to one's downfall or failure. It is a figurative expression that suggests the person responsible for the situation is creating their own problems and digging themselves deeper into a hole they cannot escape.

The idiom "diamond is forever" means that a diamond, as a symbol of love and commitment, will never lose its value or importance. It implies that the love and commitment represented by the diamond will also last forever.

The idiom "light years away" is used to describe something that is extremely far or distant, so far that it seems like it's light-years away from where you are. It's a figurative way of saying that something is beyond your reach or too far to be considered reasonable or practical.

The idiom "eat like a horse" means to eat large amounts of food very quickly, often without stopping or savoring it. It can also imply a lack of control over one's eating habits.