Are you serious - or just rabble rousing?
Very serious. If the narrative is that one is predestined to either Heaven or hell, then why should one avoid sin? From either position?
If you believe that you are predestined to heaven, then since you are going to be ultimately rewarded with salvation, why not go through life having as much self-serving fun as you can?
Else, if you are predestined to hell, why not just turn vindictive and take it out on the rest of humanity? Well?
In either case, Reformed beliefs can lead to an immediate self-serving attitude.