I have been seeking new opportunities for half a year with little sucess (I do have my old full time job). I just feel it's so difficult to remain positive after a spate of setbacks. Can anyone share their experience in how to keep positive in prolonged job search and how to keep plowing through? Thanks!

hang in there
Hi Roger,
Unfortunately, the hiring process is in no way perfect. Good folks get overlooked and poor folks get jobs they shouldn't. Not always, but frequently enough. This doesn't make it any easier to be on the losing side. Hang in there and keep your energy up. Eventually you will find something suitable.
To increase your chances,
Good luck with your search.
Kev
In reply to hang in there by Kevin Picton
Thank you, Kev and mrreliable
Thank you, Kev and mrreliable, for the comments. I thought I have done almost everyting -- networking, informational interview, tailoring resume, referrals, cold call, more education, listening to career tools etc, and the job serach still doesn't gain any traction. I am in the annual conference of my industry and I used to network like crazy in the past. But I began to develop some doubts about the usefulness. It's a really hard process.
What you're doing isn't
What you're doing isn't working. I'm not saying to completely abandon the methods you're using, but to get out of the rut you should be creative. Embrace new methods of searching for a job. If you've just been sending out resumes, start pounding the pavement. Nework. Make it a goal to come up with three or four new methods to search for a job.
Over the past 5+ years, I was
Over the past 5+ years, I was actively looking for a new position.
This entailed me improving my education (I have earned both my AAB and BSBM now), networking, going to job fairs, and interviewing at least once per week.
I would primarily focus on position that were of interest to me and also on those that would rely on my history.
In 2013 I finally purchased the interviewing series and tailored both my resume and my interviewing skills accordingly.
I had the resume workbook prior to this so my resume would almost always get me the interview, I just wasn't very effective in the interview.
I stepped into a role in February of 2014 that relied on my background and I have been very successful with it.
Next month I will be stepping into another new role (new site too) that relies on my passions and interest to be successful.
The point of this is to use all of the tools you have at your disposal and keep trying.
Do not let the frustration get to you, instead try to learn something from every stumble so that you can improve for the next one.
If possible, ask for constructive feedback from the hiring manager who says no. They give you some great pointers on how to improve.
Mac
DiSC 7121
I second what Kev said also...
Here are three suggestions (& their rationale) that you might want to consider: