First of all, you haven't forgotten how to live. Do not be discouraged. The fact that you have that seen how hollow everything is sounds to me like a moment of insight.
It might be that you feel you have forgotten what really matters. But maybe you are also beginning to understand that you never actually understood what really matters.
What we know intellectually, is one thing - but we also must ask ourselves, whenever we learn something - how does it change my world?
If I really know that everything is transient like the form taken in a wisp of incense smoke, then it's hard for me to develop an attachment to their permanence, right?
In some schools of Buddhism, there are three types of laziness - they are opposite to the three types of effort.
The first is apathy lethargy: https://www.youtube.com/watch?v=fLexgOxsZu0
The second is a lack of transvaluation: finding no pleasure in doing what is good, or finding pleasure in doing what is bad. https://www.youtube.com/watch?v=hT_nvWreIhg
The last a lack of confidence or belief in your ability to do good. https://www.youtube.com/watch?v=HDqmJEWOJRI
It is this last one which is the most harmful to our path-treading, as if we believe we cannot do it, or that it's impossible, we end up living in a shit world with no escape.
The direct opponent to laziness is effort, with the corresponding antidotes to the 3 above.
But the underlying cause of laziness is wrong view. If we are able to see the world as it is, then the natural path of least resistance is to follow the path, so developing your insight into the nature of reality is fundamental to changing the way in which you behave within it.