Low low motivation

Yesterday I went to an interview for a job. It was an interesting interview in a relaxed atmosphere and I could imagine that I could have a chance to get the job. They will decide by Jan 23rd. That job would take a lot of energy and time, a lot more than my current job does. And I have to ask myself if I really want to work more hard??? I am still searching for an answer...

But since that interview went very positive for me, my motivation in my current job is even lower now than before. I have so many things to do today but I just cannot concentrate on work and feel as if everything I do, every phone call, every document is senseless and stupid.
Is that because I see that there are better jobs available? Or is it because the end of this job is in sight? Or is it simply the midlife-crisis??? This is todays second question that I cannot answer...