Halcyon days says
Fourteen days of calm weather were to be expected when the Halcyon was nesting - around the winter solstice, usually 21st or 22nd of December. The Halcyon days are generally regarded as beginning on the 14th or 15th of December.
Now while Halcyon days may refer to peaceful days of youth -- think of long, summer days, sitting on a swing or gathering flowers when you were, say, eight years old -- its primary meaning is closer to "peaceful."
It wouldn't be wrong to say:
We're struggling now, but halcyon days are coming.
But the OP desires to use a different word (without a possible connotation of the past).
We're struggling now, but the future looks bright.
If the struggle is because of arguments:
We're fighting a lot now, but peaceful days are coming.
If the struggle is because of privation:
We're often strapped/struggling, but flush/better days are coming.
We're often poor, but days of plenty are coming.