I have decided that it would be useful to ESL learners for them to learn some idioms and popular sayings. Please feel free to post one or more yourself.
Don't count your chickens before they hatch.
"Don't count your chickens before they hatch" is a warning not to be overly optimistic. It is an admonition that you shouldn't make plans based on things you can't control.
I've got my work cut out for me.
"I've got my work cut out for me" comes from dressmaking. After the job of cutting out the pattern had been done the work of sewing the garment remained to be done. Thus, the seamstress had her work cut out for her. (She had plenty of work to do.)
Don't change horses in midstream.
"Don't change horses in midstream." Changing horses in midstream would be a difficult job indeed. Instead, it would be much better to wait until you get to the other side. You would be taking too much of a chance to change horses while you are in midstream. It would be better and safer to wait until present difficulties are over.
Don't put all your eggs in one basket.
"Don't put all your eggs in one basket" is an admonition not to take unnecessary chances. If I were advising you not to put invest all your available money on one thing I might say that you shouldn't put all your eggs in one basket.