Morning jog

Do you have days when you feel terrible but don't have a clue why? I started to have them a bit too often nowadays. I was discussing this with my mother in the morning and she told me that exercise would make my body release endorphin(happy hormone). I had learnt about this in biology this year but never thought of putting it to practice. So I put my sneakers on and went for a run and all of a sudden I wasn't feeling bad at all. I was even a little proud of myself for getting a little exercise.