I will treat all the sisters around me like how i want other brothers to treat my wife in future.
So if i do not want other brothers to flirt with my wife, i don't do it to other sisters now.
If i do not want other brothers to look lustfully at my wife, i don't do it now.
If i do not want other brothers to think of my wife day and night, i don't do it to them now.
Until the day I've confirmed who God has for me, I'll stay neutral towards all the sisters for now.
Maintaining Purity is a lifetime pursuit. Before marriage, your pursue how to maintain pure for your future wife/husband. After marriage, you pursue how to keep yourself devoted to one.