Why knit in times of stress?
It is not uncommon for someone who loves knitting to remember that a scarf, for example, was made after a breakup with someone, or after a family bereavement. It's like saying that these objects contain emotions in every "stitch." After the 9/11 tragedy in the United States, it was statistically observed that many people who had not knitted for years, and people looking for comfort in something, returned to knitting, perhaps to alleviate insecurity and ease the tension of such a grave event.
But why should one believe that knitting can be helpful during days of particular pain and stress? First of all, consider that when you knit, you concentrate (let's say you are also relatively forced to concentrate) on what is in your hands, and even if your thoughts are still present, there is still something you are creating, something that attracts your mind's attention, so that you can divert your attention from a possible stressful or tense situation, and no longer be focused on it.
Whether you do something for yourself or for someone else, knitting gently redirects your attention elsewhere, away from your stress.
The positive side is that you are creating, you are making something beautiful, and it's so different from eating chocolates or staying in front of the TV after a bad day. Furthermore, you will also have something to show for it after you've finished. If you vent by eating chocolates, what will you have accomplished?
The hope is that knitters mostly do so in happy moments, but as many knitting enthusiasts have discovered, this pleasant hobby is much more than a simple pastime to overcome difficult moments in our lives. Knitting can be compared to a new yoga, or not, but as has been said, it is a gift that you will carry with you forever.