A friend in need is a friend indeed(Yongfei Gu)

"A friend in need is a friend indeed."This is an English proverb which means 'someone who needs your help becomes friendly in order to obtain it',however,most people understand it to mean, 'someone who helps you when you are in need is a true friend'.Actually, I always thought,'someone who helps you when you are in need is a true friend' is the true meaning.

I found the origin of the proverb from the Internet as follow.

A version of this proverb was known by the 3rd century BC. Quintus Ennius wrote: 'Amicu certus in re incerta cernitur'. This translates from the Latin as 'a sure friend is known when in difficulty'.

The Oxford Dictionary of Quotations lists it as existing in English from the 11th century. The earliest version I can find is from Caxton's Sonnes of Aymon, 1489:

"It is sayd, that at the nede the frende is knowen."

The morality play Everyman also contains similar lines. The play's date is uncertain and scholars place it as 'late 15th century', which could be before Caxton's work:

Fellowship: Sir, I say as I will do in deed.
Everyman: Then be you a good friend at need.

Obviously,those are totally two different meanings. One is positive and another is negative. But why we usually mistake it as a positive one? In my opinion, when people meet a new vocabulary or a new proverb, they usually try to understand it and learn it by using them own sense;they barely consider its usage.For instance, when I learn a new vocabulary, I will try to use it in every where and even in following daily communications. Indeed, that is an optimum way to practise the language;however,sometimes I use it in a wrong way. Like the proverb above, I know the true meaning until I find the reference of it.
In addition, when we use a proverb, we must know the true meaning and the usage of it without using own sense to judge the language.