Dealing with rude patients..help!!

i work as a receptionist as a front desk istant.people who walk in as patients are mostly rude,unsmiling and sarcastic.it really irks me.we are also humans with feelings too!!! we are not here to take advantage of the clients!! we do our work and our job is not as simple as some people think.we r not dolls just to smile and sit.it really irritates me when people r rude.how do i deal with them?