It is of course necessary to be flexible but if we are so flexible that others take advantage of us it is not right. So we need to have a balance of flexibility and discipline i.e., to be flexible within the rules and code of conduct.
It is necessary to take care that the flexible nature within us doesn't waste our time or other resources. We have to be able to say no if the situation demands. But whatever we say has to be told with love, which comes when our nature is that of flexibility.