Even though you feel better, you need to keep taking the antibiotics exactly as your doctor prescribed them. It is important to take all of the medication because there may still be harmful bacteria within your body. If you don't finish the antibiotics, some of the dangerous bacteria may not die and you might get sick again. The bacteria that are still alive can then become resistant and make the infection you already have, even harder to treat.
By not finishing your medication, you are also putting the health of other people at risk. Antibiotic resistance affects everyone, not just people who don't use antibiotics properly. When antibiotic medication is stopped before the entire prescription has been taken, the surviving bacteria may become "resistant bugs", which are bacteria that are less vulnerable to common treatments.