Why was my cider made from apple juice so bad

I tried to make cider from shop bought apple juice which was 100% pressed wih no chemicals in it.but when it had been in the the bottle for four weeks i tried it but it was horrible.should i have added anything to the apple juice. what do other people do when using apple juice.

Can you provide more details?

Did you measure a FG?

Does horrible mean too dry, bitter, sour, thin, funky?

What kind of yeast did you use?

How long and at what temperature did it ferment?

I didn’t check fg as i haven’t got equipment to do that.i don’t check it normally and i have never had any problems.i would say it tasted too sour.it was probably fermenting for two weeks.i would say the temp was between 18°c-20°c.do i need to ferment it longer.

I think i used a youngs cider yeast