If you use a commodity or resource carefully and without extravagance you will never be in need.
This explanation given by the Oxford Dictionary seems to imply that one does not only need to be careful with how to use material things but that the same care should be taken with immaterial resources like time, energy and talents.

In our current economic climate, or better said the current global economic recession we are hearing more and more again the phrase: waste not, want not. In my English newspaper I can read a lot of stories about how England during and after the Second World War managed almost complete self-sufficiency with this motto. People were growing their own food not wasting the smallest plot of land and nothing was put to the bin until it could no longer be mended or reused.
I like this motto and think it was high time that our spending spree of buying more and more new stuff came to an end. But this global recession is bringing a whole new kind of waste.

How many of us are now wasting their time and energy with worrying about the future, blaming others for their situation or fighting for things to stay as they where? Just think of the many opportunities missed because governments and financial institutions are busy trying to hang on to what is gone? What opportunities are you and I missing while we are caught up in our fights, blaming games or worries? When will we realise we should not only be careful with how we use material things but use that same care with our immaterial resources like our time, our talent and our energy? The more time, talent and energy we waste the worse it will get.
The only question that remains is how much worse will it have to get before we realise this one?