In many ways Twilight could call herself a very fortunate mare, perhaps more fortunate than she deserved. Having a relationship with the kindest, most loving and most beautiful pony in all of Equestria was one of those ways. Better still, the flames of their love ignited on the same week of the month, right down to the day. It was common for mares who took their heat week off to take the day before it off as well; for Celestia, the court was closed to give way for an office day of peace and near-solitude, which Twilight always made sure to spend with her.
If estrous was a raging firestorm of lust that burned away all other thoughts and left only the purity of carnal bliss, the day before was the calm preceding that storm: a gentle flame, the kind that blanketed you with its soothing warmth and could lull you off to a pleasant rest, yet with a budding spark just beneath the surface, tensing, gathering its fuel before it finally blazed with all its might. For Twilight, too aroused to want to leave Celestia’s side but not yet aroused enough to actually do something about it, the simplest and most mundane of things seemed even more magical, shimmering in burning mirages as if they were part of a dream.
Walking through the palace halls was just like a leisurely stroll along a warm beach. Drifting, nearly aimless, filled with as many little snuggles as they could get in without tripping over each other and the occasional tease of so much more, while all the wonderful ponies around them glowed incandescently; Twilight could only wish they too knew the kind of love they shared. Waiting for Raven to return with something they asked for, or pondering on how to respond to one missive or another, was just an excuse for fire to dance between their writhing tongues. Eating lunch was less about the food and more about their endless giggling at jokes that weren't actually all that funny while their minds wandered over the round, smooth shapes of the vegetables, constantly reminded of all the hot things they would do to each other the following evening. It didn't matter what they did; as long as they were together life was perfect.
When the night was still young they stoked their flames in bed together, smoldering with slow foreplay before kissing each other to sleep. Twilight knew they would see each other in flaming dreams, eagerly awaiting the next morning when their desires flared to a prominence only this blessed week could give them--only then the real fun would begin.