There are plenty of fish in the sea
there are plenty of (other) fish in the sea
There are many other excellent or more suitable people, things, opportunities, or possibilities in the world that one may find. Said especially when one has recently been unlucky, unsuccessful, or has broken up with a romantic partner. I know you are broken up about Janet leaving you, but there are plenty of fish in the sea. I'm pretty disappointed that I didn't get the job, but I'm trying to remind myself that there are plenty of other fish in the sea.
There are plenty of (other) fish in the sea.
Fig. There are other choices. (Used to refer to persons.) When John broke up with Ann, I told her not to worry. There are plenty of other fish in the sea. It's too bad that your secretary quit, but there are plenty of other fish in the sea.