The idiom "alma mater" refers to an alma mater school or university. It is often used as a term of endearment for one's school or university, particularly when referring to its graduates.

The idiom "the course of true love never did run smooth" means that the journey of true love is often full of obstacles, difficulties, and challenges that make it difficult for lovers to be together.

The idiom "the best is yet to come" means that there is something better or more positive that will happen after what has already happened. It suggests that the best things are yet to happen, and they will occur in the near future.

The idiom "make a virtue of necessity" means to turn a difficult or unpleasant situation into an advantage or positive outcome. It implies that the person is taking action in response to circumstances beyond their control and is finding a way to make the best of it.

The idiom "water under the bridge" means that something has happened or occurred in the past, and it's not relevant to what is happening now or in the future. It's a way of saying "let's move on from the past.