Scientific research is a real complicated venture. Some days your experiments work and you are on a roll. On other days you never observe what you were expecting. This is not necessarily a bad thing, many phenomena were found this way either as something that hindered an experiment from working or as a mistake. Sometimes when you cant see things go your way in the lab you try again and again and again but if the trend is not seen again it might have been just a fluke! Sigh!
You cant continue wasting time and money on something that cant be reproduced so what do you do? You move on to another project, something else that shows better results and a promise of a real find in the future. Most researchers know this but when it actually happens in your work you feel like you are giving up and maybe if you would run the protocol one more time you would see good results ...at least I do. My work is my baby its just hard to move on after a failed attempt but hey you learn from it and re-doing it a hundredth time is not going to make something magically appear. Moving on doesn't mean giving up on the project or forgetting it. It means while you work on other scientific endeavors you keep the other idea at the back of your head, at the back burner. Who knows maybe one day you might come back to it with fresh eyes and new perspectives.
I guess the same applies to other things in life, sometimes if things are not working its better to move on. Being stuck and obsessing on the same thing does not help change it. New ideas come while you are already working