It sounds harder than it actually is, you can always adapt to your personal situation, but if one always does only 15 minutes "jog, jog, jog", two times a week,

It sounds harder than it actually is, you can always adapt to your personal situation, but if one always does only 15 minutes "jog, jog, jog", two times a week, without challenging himself and higher-tempo parts, that will not be enough for "runner's high". One has to put some effort into it, before you can reap.