Bhagavad Gita Verse 14, Chapter 12

santushtaha satatam yogee yataatmaa dridhanishchayaha |
mayyarpitamanobuddhiryo madbhaktaha sa me priyaha || 14 ||
 
The yogi who is always contented, self controlled, with firm conviction, who has dedicated his mind and intellect to me, he who is such a devotee of mine is dear to me.
 
santushtaha : contented
satatam : always
yogee : yogi
yataatmaa : self controlled
dridhanishchayaha : firm conviction
mayi : to me
arpita : dedicated
manobuddhihi : mind and intellect
yaha : he who
madbhaktaha : my devotee
saha : he
me : me
priyaha : dear
 
Most of us derive contentment from people, objects and situations in the world, most notably after consuming a delicious meal. Contentment is a state where the mind does not want anything else from the world. But, this state is temporary because the contentment has been triggered by something that is temporary and finite, like food for example. Shri Krishna says that the yogi, the perfected devotee, derives contentment from Ishvara within himself, therefore he does not need to become a bhogi, one who runs after material objects for contentment. He is “satatam santushta”, even contented.
 
Another quality of a perfected devotee is a firm conviction that only Ishvara exists, and that the world does not exist independently of Ishvara. Most of us assume that the world has an independent existence. We attach all sorts of values to it. causing our intellect to generate innumerable goals and convictions around those values. The perfected devotee sees only Ishvara everywhere, and therefore is ever steadfast in his conviction that only Ishvara exists.
 
This “dridha nishchaya” or firm conviction is demonstrated by the devotee’s submission of mind and intellect in Ishvara, and also, the control of the mind, body and senses. When the intellect is convinced that only Ishvara exists, and when the mind thinks only of Ishvara, the devotee does not need any other special yogic technique to control the organs of action and the sense organs. Selfish desires are the cause of the mind, body and senses deviating from prescribed actions. When there is only the desire for Ishvara, they can never deviate. Shri Krishna says that the perfected devotee is a “satatam yataatmaa”, one who has complete self control at all times.
 
Here Shri Krishna concludes the line of thought that he began in the previous shloka by asserting that the devotee who has inculcated these traits is very dear to Ishvara. These eight shlokas starting from the thirteenth shloka are one of the most famous and beloved shlokas in the Gita.

Bhagavad Gita Verse 7, Chapter 8

tasmaatsarveshu kaaleshu maamanusmara yudhya cha |
mayyarpitamanobuddhirmaamevaishyasyasamshayam || 7 ||
 
Therefore, remember me at all times and fight. One who offers his mind and intellect to me attains me only, without a doubt.
 
tasmaat : therefore
sarveshu : all
kaaleshu : times
maam : me
anusmara : remember
yudhya : fight
cha : and
mayi : to me
arpita : offer
manaha : mind
buddhihi : intellect
maam : me
eva : only
eshyasi : attains
asamshayam : without a doubt
 
Shri Krishna gives the ultimate teaching to all of mankind in this shloka. Since the thought at the time of death determines our fate after death, and the thought of death is an outcome of our lifelong thinking, Shri Krishna instructs us to remember Ishvara at all times and perform our duties.
 
Let us examine this instruction further. We are not asked to give up our duties, retire to a forest and constantly think of Ishvara there. Shri Krishna wants us to first remember Ishvara, and then perform duty consistent with our svadharma. The result of leading such a life is that we will attain Ishvara certainly. There is no doubt in this matter.
 
With this instruction, meditation takes on a whole new dimension. Typically, we confine meditation to something that we do for fifteen to thirty minutes, sitting in a solitary place as instructed in the sixth chapter. We now realize that those instructions were meant to prepare us for the kind of meditation that Shri Krishna wants us to pursue: 24/7 meditation of Ishvara.
 
How can this be possible? Our mind can only think of one thought at a time. So the way to meditate continuously is to somehow understand that everything we see, do and know is Ishvara.
 
Now we understand why Shri Krishna defined the terms brahma, karma, adhibhuta, adhideva, adhyaatma, adhiyagnya at the beginning of the chapter, because all those are nothing but Ishvara. If, while performing any action, we know that the actor, the action, the instrument, the process and the result - everything is Ishvara - we will never forget Ishvara.
 
Even if this kind of thinking is not possible for us in the beginning, we can emulate the mind of a mother who, regardless of what she is doing, always thinks about her child in the background. By practising meditation on our favourite deity we develop an attachment to it, so that we can recall it every time we feel distant from Ishvara.
 
So therefore, by practicing meditation constantly on Ishvara, we should strive to change our thinking such that our final thought will be nothing but Ishvara. This constant meditation upon Ishvara is called upaasanaa.