Being happy is not something that we can take for granted, problems can derail our happiness at any time.
But we can take steps to ensure that we are aware of the causes and take steps to resolve and correct the effects.
Sensei summed it up perfectly …
Buddhism teaches that we are each responsible for our own happiness or unhappiness. Our vitality—the amount of energy or “life-force” we have—is in fact the single most important factor in determining whether or not we are happy.
True happiness is to be found within, in the state of our hearts. It does not exist on the far side of some distant mountains. It is within you, yourself. However much you try, you can never run away from yourself. And if you are weak, suffering will follow you wherever you go.
You will never find happiness if you don’t challenge your weaknesses and change yourself from within.
So if you are happy with life at present, be mindful of where that happiness comes from. If you are unhappy, challenge the causes of that unhappiness and make the changes you need to make.