I lost my motivation at work. How do I put myself the same motivation I had at first?

Don’t know why, but the last month I lost all my motivation. I was so excited about what we are doing here and now its like I am not sure any more if this effort really worthwhile?

I thought I should go on a vaction but I’m not sure it would help.

Did it happen to you too? What did you do?
I feel like I lost all my energy to come every day to work :-/