Beingoptimisticmeansbeinghopefulaboutthefutureandthesuccessofsomethinginparticular.Beingpessimistic,ontheotherhand,meansbeingsadaboutthefutureandalwaysthinkingthatsomethingbadisgoingtohappen. 　　Let’stakethechallengesinoureverydaylifeasanexample.Facedwithachallenge,apessimisticpersonmayfeelgloomy,distressed,andevenafraidofit.Heconsidershimselfpowerless,andcomplainsaboutitalldaylong,refusingeventohaveatrybeforegivingitupintheend.Anoptimisticperson,however,mayadoptanentirelydifferentapproach.Hemaynotregardthechallengeassomethingbad,instead,hetakesitasanexcellentopportunityto 　　displayhisabilitiesandtalent.Pressuresimplyaddstohisenthusiasmtorealizehisdream. 　　Obviously,beingoptimisticandbeingpessimisticaretwodifferentattitudestowardslife,whichalwaysmeanthedifferencebetweenfailureandsuccess.Itisnaturalthatweencounter 　　challengesofonekindoranotherinourlife.Ifwearepessimisticwheneverweareconfrontedwithchallengeswearedestinedtohaveonefailureafteranother.Ifwearepessimistic,wearedestinedtofail,endingupaccomplishingnothing.Butifweapproachthe 　　challengesinanoptimisticway,wemaygofromvictorytovictory. 　　Therefore,beoptimistic,allthetime. 　　本文第一段宜采用下定义的方法给出乐观和悲观的含义；第二段采用对比的写法,列举两种人对待挑战的态度,来说明乐观和悲观；第三段进一步说明乐观和悲观会产生不同的结果,自然得出我们应乐观的结论.