1. Always finish your course of antibiotics. Even if you're feeling better. The course is as long as it is for a reason. 2. If for some reason you choose not to do (1) above, do not ever give someone what is left over from your course.
[1] https://www.mja.com.au/journal/2015/202/3/knowing-when-stop-...
Also, don't take antibiotics yourself unless you are certain they are necessary; many infections are non bacterial, and even some bacterial infections can be fought off by your body quite well. Look after your immune system; it looks after you.
Ironically, taking antibiotics might negatively impact your immune system due to the impact of the antibiotics on your intestinal floral (mostly bacteria, a lot of which are killed during the course), which are increasingly being linked to healthy immune function.
Ask your doctor what happens if you don't take antibiotics - are they really needed for this illness?
If you do get antibiotics take the full course. Take them correctly, according to the instructions.
One possible reason not to worry is antibiotic cycling. Bacteria lose their resistance to individual antibiotics when we stop giving them exposure to them, so the idea is that we could breed out old resistance while breeding in new resistance and always have a drug available that they're defenseless against.
> Congress should instead reward manufacturers that bring a targeted, highly innovative antibiotic to market with a substantial financial prize; in exchange, manufacturers would surrender their patent.