The toddler's quality of life is completely dependent on & controlled by his external circumstances. He reacts automatically - almost machine-like - to his environment. Such reflexive reactions typically bring about "short-term gain", which we realize at some point, usually comes with "long-term pain." Reactivity can remain a dominant, destructive force throughout one's entire life.
A very wise individual's quality of life can be stunningly independent of external circumstances. See: http://mindfulnessforeveryone.blogspot.ca/2013/11/431-transformative-power-of-acceptance.html Instead of reflexively reacting to environmental changes, they experience a gap in time, during which they can choose from a variety of possible responses ranging greatly with respect to the probable long-term effects on themselves, others & the environment. The wisest choice is that which is thought to bring about the most long-term improved quality of life, & least amount of suffering for all concerned. When wisdom is the highest priority, true happiness & peace arise.
Reactivity increases from reacting mindlessly to situations. Wisdom increases from responding wisely to situations. Whatever we choose to train in, becomes stronger & easier to use. Prolonged patient continuous mindfulness practice inevitably leads towards greater wisdom-based happiness even under the most challenging situations.
So we always have a choice: prioritizing the practice of minding our mind - OR - allow the mind to continue running on autopilot?
"Our true nature is far more ancient and encompassing than the separate self defined by habit and society. We are as intrinsic to our living world as the rivers and trees, woven of the same intricate flows of matter/energy and mind. Having evolved us into self-reflective consciousness, the world can now know itself through us, behold its own majesty, tell its own stories, and also respond to its own suffering." Joanna Macy
The wisdom level of our consciousness ("the wise grandparent") is inherently part of us. The often dominant autopilot reactivity ("self-centered todler") is ALSO an inherent part of us. We need to explore, get to know & accept ALL aspects of ourself (all our subpersonalities) and thus gradually stabilize in the wisdom level of our consciousness.