Effects of bad review


Hi Guys !!
I have been more than 7 months on fiverr sometimes it goes good beyond our expectations and sometimes i am down that probably caused by bad review and 1 bad review can’t be invaded by even 15 complete 5 stars reviews.
can anyone guide me how to prevent the effect of bad review for sooo long or is there any effective way to get cope with it please ??
Many thanks guys !!!