Destiny is not something that comes down from heavens or springs up from our birth chart. On the contrary, we create our destiny by our actions with our free will in the past lifetimes.

God is seated within us, and he bestows upon us the power to act. However, using our free will, we decide what we do with that power. This is just as the utility provider supplies power to our house. Once we have the power at home, what we do with it is or own choice. We could operate a fan or lamp, or heat and cool the house, as we wish. Similarly, for example, God gives our eyes the power to see, but what we see is our own choice. We could go to the temple and have the darshan of the deities, or could go to a theater to watch a movie. God just gives us the faculty of sight; he doesn't decide how we use it. 

God is neither the director of our actions, nor does He decree whether we will perform a particular virtuous or evil deed. He is not responsible either for anyone's virtuous deeds or sinful actions.

God's work in this regard is threefold: 1) He provides the soul with the power to act. 2) Once we have performed actions with the power supplied to us, He notes our actions. 3) He gives us the results of our karmas.

One may ask why God grants free will to the soul. It is because "the soul is a tiny part of God and it possesses His qualities to a minuscule extent. God is abhigña swarāṭ (supremely independent), and so the soul also possesses a tiny amount of independence to utilize its senses, mind, and intellect in the manner it wishes," elucidates H. H. Swami Mukundananda ji.

We humans are bound by the law of karma, but understand the principle of free will through the example of the bow and arrow in archery. The accumulated stock of arrows in the archer's case slung over his shoulder is the sañchit karma. Similar to this is our stock of karmas from past endless lifetimes. A part of the sañchit karma is the prārabdh karma that we have to bear in this life. Therefore, the arrow that has just left the archer's bow is the prārabdh karma and the arrow in the hand at the moment is kriyamāṇ karma, this is the karma we are free to perform in this life. The archer can decide not to use this arrow, or he can choose to use it either to protect the weak or to harass them. Thus, while prārabdh karma is something which cannot be undone and we have to enjoy or suffer its fruits in this life, we have free will available in the form of kriyamāṇ karma.

Right here in the present moment we possess the free will to perform actions that elevate our consciousness to sublime heights or perform actions that degrade us to demonic existence. The choices that we make in the face of adversity or favorable situations are ours. Hence, the scriptures say that it is lazy people who blame destiny for their substandard achievements:

For more on this topic, see Forge Your Destiny with Every Thought.