Lending

In Matthew 5:42, why did Jesus encourage his disciples to lend to the borrower and not turn him away? We have all lent something which was not returned. We become reluctant to lend again. Did Jesus mean that we are to keep lending until we have nothing left? That is how some criticize Jesus. He spoke of one borrower, not an unlimited number. Our natural inclination is not to lend at all or with very few exceptions for family or close friends. It is that extreme that Jesus challenged. He challenges us also to consider lending without discrimination. Of course there are boundaries and limitations, but perhaps we could lend to at least one.