As Buddha said—wherever you go, there you are.
The world, to a considerable extent, is a reflection of ourselves. Science has determined that we are all born with an inherent baseline of happiness and we hover around it for all our lives. In other words, you will only ever be so happy in your life.
If you can stop desire and let go of attachment to outcome, life becomes about the moment; until then, however, it is about the past or the future.
And we all have our own angle of repose.
The angle of repose is an engineering term; it represents the angle at which piling more sand (or any granular material such as sand) on a pile of sand will no longer raise it. Instead, what happens, when the angle of repose is exceeded, is that the sides fall away. The pile collapses.
But the term also has another meaning wherein it refers to the maximum angle at which an object can rest on an inclined surface without sliding down: Mountain climbers use it in to analyze the likelihood of an avalanche.
My point is that we all have our own angle of repose—it is the point at which, if we pile one more thing onto our life, the pile itself might well give way. Emotions, feeling, tragedies, despair can all pile up and cause just such a collapse.
And just as we are all bound by the natural laws such as gravity, we are all bound by our own, individual angle of repose and, if you exceed it, your life could well begin to slide away.
A mountaineer will bet his life on his judgment of the angle of repose. Your life might depend on your judgement of it, as well. The slope of a gentle soul is tenuous.
Be aware of your personal angle of repose and be sensitive to it. Moderation, equilibrium, and balance in all matters will work best in this regard. And understand, too, that desire is the most granular of materials.