Complacency is a form of sloth/torpor. Complacency can be said as lethargy in the body (sloth) and drowsiness in the mind (torpor). It is when the mind is not sleeping, but not awake either. So be aware of this twilight zone, where nothing of use is achieved. Buddha advises us to be aware of this enemy in life that would stop you from succeeding in life. So we have to make a habit of getting up early every day, being energetic. Energy arises when one has a clear-cut direction. One knows exactly where one is going and keeps at it. This is one to keep Mara’s armies at bay.
The host of Mara, the Evil One, is described as comprising ten kinds of passions (kilesa). They are: 1. material pleasures (kama). 2. aversion for the Holy Life (arati), 3. hunger and thirst (khuppipasa), 4. craving (tanha), 5. sloth and torpor (thina middha), 6. fear (bhaya), 7. doubt (vicikiccha), 8. detraction and obstinacy (makkhathambha), 9. gain (labha), praise (siloka) honour (sakkara) and ill-gotten fame (yasa), 10. Extolling of oneself and contempt for others (attukkamsana-para-vambhana).
On The Five Mental Hindrances and Their Conquest and specially on sloth and torpor (thina middha) following is a good example:
Once when the Venerable Maha Moggallana, one of the Buddha's two chief disciples, was meditating in the forest, thina middha arose. His mind shrank and withered, as unworkable as a piece of butter that hardens in the cold. At this point Supreme Buddha looked into the Venerable Maha Moggallana's mind. Seeing his plight, he approached and said, "My son Maha Moggallana, are you drowsy, are you sleepy, are you nodding?"
The elder replied, "Yes, Lord, I am nodding." He was frank and candid in his reply. the Buddha said, "Listen, my son, I will now teach you eight techniques of overcoming sloth and torpor."
Some of the eight Ways to Stay Awake are… first is to change one's attitude. When torpor attacks, one may be tempted to surrender to thoughts like, "I'm so sleepy. It's not doing me any good just to sit here in a daze. May be I'll lie down for a minute and gather my energy." As long as you entertain such thoughts, the mental state of sloth and torpor will be encouraged to remain. If, on the other hand, one states decisively, "I'll sit through this sloth and torpor, and if it recurs I still won't give in to it," this is what the Buddha meant by changing one's attitude.
If you are content in life is easier to overcome these subtle barriers, these “hindrances,” or “obstacles” as they’re self-created.
Contentment counters sensual desire that the Buddha compared to debt. He compared Ill will to a sickness or an illness. Sloth and torpor he compared to a prison. Restlessness and anxiety he compared to slavery. Uncertainty he compared to traveling across a barren, dangerous landscape.
Contentment is to be content about everything else - all other aspects of your life, but NOT of your spiritual development. Your liking for the Dhamma Path should far exceed the liking that you have for all other things. Then only Contentment can be taken as being detached. The term detachment gives a much deeper meaning than just non attachment. It is used in Dhamma to denote a certain state of mind, which characterizes calmness, serenity, and equanimity. One become thus by being detached from both aversion or revulsion, and attachment. The absence of the five hindrances - namely; sensuous desire (kamacchanda), ill-will (Vyapada), sloth and Torpor (thinamiddha), restlessness and scruples (uddhacchakukkuccha) and Skeptical doubt (vicikiccha) helps one to arrive at such a state of mind. A content mind which is neither attached to anything nor repulsed by anything, helps one to dwell in calmness, coolness, and serenity of mind. A state of calm,detachment is a very positive state, unlike complacency.