Well... First we'd need to find the use.
A vacuum is useful when it does what it's supposed to do: cleaning your apartment well.
A hammer is useful when it does what it's supposed to do: hammering nails into the wall.
A vacuum is useless when it is used to hammer nails in the wall...
(Sidetrack alert!) So what is the use of a human? What is its purpose of life?
I don't know... Nobody knows... I don't think there even is one...
So if we are to discuss the usefulness of life, then we'll firstly have to define what the use of life is. (Or if there is any.) (End of sidetrack)
As for the usefulness of everyday life, this is alot easier: it is useful (if done properly).
According to the sociobiological anthropology put forth by Richard Dawkins, genes, and therefore you yourself (albeit unconciously), will focus on surviving, at every minute of every day...
Now... Everyday life generally consists of 2 things: working/schooling, and enjoying yourself/socializing. And what's the purpose of these things?
School prepares you for a good job with which you can earn good money, with which you can in turn, survive better than with a shitty job.
A job (as said above) earns you money, which increaces your chances of survival more so than, say, being a beggar.
Socializing gets you friends, who will (hopefully) protect you when you're in trouble (be it physically, mentally, financially, etc.). AND it puts you in a position where you can meet potential mates...
Having fun/doing hobbies makes you content, happy, and therefore, it makes you more friendly and attractive (have you ever been in love with a sadhorn? I think not). Therefore ensuring more friends, maybe even a mate. But more importantly: less stress, and therefore a healthy mental state. 'Cause let's face it: you're only going to jump in front of the train if you're depressed... Which having fun should prevent. Again: survival chance jumps up.
In short: everyday life's unconcious and ultimate purpose/use is to give you a better chance for survival.
Conclusion: whether your everyday life is useful or not, depends solely on the person. If YOU fulfil the use of everyday life, then your everyday life is useful. If not, THEN, and ONLY THEN will it be useless...
Do note, however, that this is only and just the sociobiological viewpoint of psychology and the explanation to everyday life... This is my preffered anthropology, simply because it makes so damned much sense, and I have therefore selected this one to counter your statement of 'everyday life... useless!'.
But it could be wrong...