You stare at the computer screen. Knowing that you need to get that next card completed in the current sprint, but somehow you are struggling to muster the energy to do it. That card just sucks. The discipline to overcome your internal impediment is not there, and you find yourself wandering over to open and read The Onion instead. Just one more story you tell yourself...
There are many ways in which we experience stress. I will make a few metaphors here to create a visualization of my concept here. The first of which is a spring. Consider a slow motion spring. A stressful event will begin to compress the spring. When the spring is compressed, it does not have more give to give. In the usual run of things and our every day stresses, it doesn't compress very far, no where near our actual limits and will generally naturally decompress. There are times where we struggle. The spring isn't bouncing back like we expect it to normally. When the spring is flat we find it difficult to operate normally. I would also say that we have multiple independent springs, mental, emotional, and physical (there may be even more, hormonal/endocrine, etc). If any of them are flat, our general performance will dive and if some are exceptionally strong it can help out some of the others a small bit. The physical spring is generally one of the most understood. You have a workout or get injured (compress), then you rest with low activity and sleep as well as provide your body with good nutrition and in time you recover (decompress).
Consider a more extreme example of some of the other springs. In this hypothetical example I went out to lunch with some co workers and we had a good time. On my way back, as a pedestrian I almost get hit by a truck going 40 mph. I come within a hairs breath of just being dead or the next thing to it after lunch. I have several seemingly slow motion moments of seeing the truck and then some combination of my moves and the drivers results in me just being missed. I get back to the office. I'm mentally and emotionally tied up in knots trying to process the event. A couple of my springs are pretty flat at this moment, primarily emotional though you may also have a hormonal decompress coming. Am I going to just be able to shake it off and work? Unlikely. I believe that these springs do work like muscles, the more and deeper that you use them the stronger they get. At least when they are springing back to a healthy normal with a generous amount of give, you get stronger.
In this extreme example we are in a very flat or compressed state. How do we cope with it? One of the primary methods in our culture is numbing. This is illustrated in the opening example. We don't like the flat state so we hide from it by doing something nominally enjoyable but with the real purpose of covering up or distracting us from contemplating our flat and stressed state. This can be a chemical numbing via drugs. A pleasurable numbing via food, stress eating. Or a multitude of other activities, movies or TV shows, games, chats or social media, and reading interesting novels or websites, etc etc.
The material point is that this numbing does not really help us actually decompress the spring. They aren't productive activities, and moving us forward, but with them we are trying to avoid something unpleasant (which need not be as extreme as the above example). With them we are not processing the event to move beyond it, we don't make any progression forward in our works either. This realization that we are not being productive but consuming time with a fruitless pursuit becomes another stress point to put on top of the original source we are trying to avoid. Then the compulsion to remain within the numbing activity just ratchets up and we enter a compulsive cycle that gets harder to exit rather than easier over time. This is what many addicts experience.
Continued productivity depends on avoiding even the minor contributors to the numbing cycle. To do that requires that you identify your personal numbing behaviors and don't even start them, to know them for what they are. I believe that the surest keys are that you sort of enjoy it but also find the behavior compulsive. The primary purpose can be seen as masking something else rather than the savor it provides. You want to do it again, again, and it takes some will power to stop. These are items that you should blacklist in your life. Avoiding them entirely will enable you to make room for both the works, and the truly enjoyable activities and relationships that will much more readily decompress your springs.