yuktaahaaravihaarasya yuktacheshtasya karmasu |
yuktasvapnaavabodhasya yogo bhavati duhkhahaa || 17 ||

One who has regulated his intake and movements, his conduct in action, his sleep and wakefulness, his sorrows are eliminated through yoga.

yukta : regulated
aahaara : intake
vihaara : movement
asya : one who conducts
yuktacheshtasya : one who is well behaved
karmasu : in actions
yukta : regulated
svapna : sleep
avabodhasya : one who is awake
yogaha : yoga
bhavati : are
duhkha : sorrow
haa : eliminate
In several places within the Gita, Shri Krishna explains a point by highlighting both its positive and negative aspects. Previously, he advised the seeker against pursuing extensive austerities using the body. In this shloka, he urges us to lead a well balanced and regulated life so that our body can support our spiritual endeavours. He says that one who has a well regulated diet, exercise, conduct and sleep is fit to become a meditator. Meditation destroys sorrow when one leads a regulated life, but it can very well cause sorrow if one does not.
As we saw earlier, Shri Krishna advises us to monitor the quantity and quality of our food intake. We should be constantly aware of what we are eating, how often we are eating it, what will be the impact on our meditation and so on. On similar lines, the level of daily activity conducted by our body should be appropriate with regards to our health, job and so on. If we lead mostly sedentary lives, then we should undertake the right level of exercise so that meditation does not make the body less active. If we lead very active lives, then we need to ensure that our body is calm and rested when we attempt to meditate.
Furthermore, the quality of our actions also determines success in meditation. If we have the habit of getting into fights with people, we will not be able to meditate properly because the fight will pop up during meditation. Similarly, if we watch a lot of tv or read a lot just before meditation, those inputs will manifest as thoughts and disrupt the meditation. The need to have the appropriate amount of sleep is also re-emphasized.
Broadly speaking, we have to decide what takes priority in our life. If material pursuits take priority, then there always will be excuses and reasons why our meditation cannot happen properly. But if meditation becomes the primary priority, then not only will we progress on the spiritual path, but the well-regulated life that results out of the discipline the we gain becomes a welcome addition.