Why human always have expectation about something in the future?

think of it this way...everyone goes to school 5 days a week and those 5 days are filled with hard work frustration tiredness and difficulty..but you get through those 5 days and work your best because you have the weekend to look foward too.. and you get through alll that studying because you have a good college ducation to look foward too... if you didnt think about the future you would have no reason to keep going those 5 days of the week because you wouldnt think about how fun the weekends would be or anything like that.. well this is so confusing and you probably dont understand it but thats alrightt.. i tried haha