According to my opinion, If you a new guy to fiverr, don't make any argument with your clients. First you must getting know how to deal with a buyer. try to make a mutual relationship with your clients. some people are really tough. before earn dollars your must earn your buyer bro. Don't disappointed about this case. If he leave a bad review, it's hard to recover. Don't try to cancel any order if you don't have fair reason. it will affect to your gig rating. If you have such type of situation, contact cs asap.
You have to sacrifice your time and sleep if your need to become a good seller on fiverr. because this is a huge arena. if you want to become a good fighter in there, You have to earn it intelligently.
Don't give-up. "Don't work hard, Work smart" Do your job very well.