The sun can give heat and light to the whole world, but he cannot do so when the clouds shut out his rays. Similarly as long as egotism veils the heart, God cannot shine upon it.
Imagine a limitless expanse of water: above and below, before and behind, right and left, everywhere there is water. In that water is placed a jar filled with water. There is water inside the jar and water outside, but the jar is still there. The 'I' is the jar.
One cannot completely get rid of the six passions: lust, anger, greed, and the like. Therefore one should direct them to God. If you must have desire and greed, then you should desire love of God and be greedy to attain Him.
Make your meditation a continuous state of mind. A great worship is going on all the time, so nothing should be neglected or excluded from your constant meditative awareness.
A man develops a subtle power as a result of the strict observance of celibacy for twelve years. Then he can understand and grasp very subtle things which otherwise elude his intellect. Through that understanding the aspirant can have direct vision of God. That pure understanding alone enables him to realize Truth.
To work without attachment is to work without the expectation of reward or fear of any punishment in this world or the next. Work so done is a means to the end, and God is the end.
You speak of doing good to the world. Is the world such a small thing? And who are you, pray, to do good to the world? First realise God, see Him by means of spiritual discipline. If He imparts power you can do good to others; otherwise not.