Keep applying

The best thing to do when applying for a job, is to keep applying... even if you have an interview. Just keep applying; I didn't do this for a long time and I would just get turned down interview after interview.
But, once I got an interview. I would stop applying for jobs, I think it was a bit of thinking I would get the job and so I wouldn't have to apply anymore. But that's not the case, not for me at least and not for many other people either. By stopping, you're just slowing yourself down and hurting yourself by getting a (possible)  failure. You have to continue until you win, you can't stop for anything... well except if you get the job, then you can stop; unless you need more than one job.
If you do by chance get a job and still have interviews, just call or email the company back that you've obtained something else. I've done this before for a company that I found unsavory; had I known what the company was, I would never have applied for it. So, when they posted their website after emailing me with their interest and I checked it out. I found that I would NOT have enjoyed it there at all, because it was a religious company and I do not agree with religion, so I wouldn't have been very pleasant working there.
So, I just told them that I obtained employment... now I just have to make sure I know what their ad looks like on craigslist lol.
I also said that for the school I voluntarily worked at for a week.