... is unlimited.
It doesn't really matter anymore tomorrow how much time, money, energy and resources you've already put in.
Especially, if tomorrow the thing you've worked so hard for will be worthless.
Or if it's something that doesn't really make you happy anymore.
Even worse, holding on to the past will rob you of future opportunities, relationships and happiness.
The time, money, energy and resources you've already put in don't really matter.
What matters is what the benefit of putting in more time, energy and resources will be.
And if it's zero or less than putting them into something else, then just go ahead and do something else.
Of course, the hardest part is about being honest to yourself and realizing that it's probably going nowhere....