Today . . . tomorrow

Hi everybody. I have a question if you could help me with. In my native language there is an expression which can be translated in "word by word" way, like "from today to tommorow".

This is used, for instance, when someone wants to express that he barely has enough to make a living and it is like "he lives from today to tommorow".
Another usage would be when expressing that nothing can be steadily learnt too easy or too fast, so it is used like "nothing can be learnt from today to tommorow".

Hoping that I managed to make myself clear, I would appreciate if anybody tell me some similar English expressions, and I mean some well-known sayings.
Thanks in advance!

Regards
iulian

"Living hand to mouth", or "living paycheck to paycheck" are English expressions that describe a situation where a person is struggling to make a living.

"Rome was not built in a day" is an expression used to convey the idea that a task can not be quickly accomplished.

He doesn't know where his next meal is coming from.

"One day at a time" is a popular expression to describe the way to cope with a difficult situation that will exist for a long time or forever.