Proust considered his time in the military as among the happiest of his life. We get a glimpse of why this may be in the passages where Marcel visits Saint-Loup at Doncières. One is struck by the protagonist’s uncharacteristic delight in physical existence, which intensifies his senses.
If I wished to go out or come in without taking the lift or being seen on the main staircase, a smaller private staircase, no longer in use, offered me its steps so skilfully arranged, one close above another, that there seemed to exist in their gradation a perfect proportion of the same kind as those which, in colours, scents, savours, often arouse in us a peculiar sensuous pleasure. But the pleasure to be found in going up and downstairs was one I had had to come here to learn….when I set my feet for the first time on those steps, familiar before ever I knew them, as if they possessed, stored up, incorporated in them perhaps by the master of old whom they used to welcome every day, the prospective charm of habits which I had not yet contracted and which indeed could only dwindle once they had become my own. (III,103)
To reach the training ground I used to have to make long journeys on foot….And when I wanted to get up I had a delicious sensation of being incapable of doing so; I felt myself fastened to a deep, invisible soil by the articulations (of which my tiredness made me conscious) of muscular and nutritious roots. I felt myself full of strength; life seemed to extend more amply before me; for I had reverted to the healthy tiredness of my childhood at Combray on mornings after the days when we had taken the Guermantes walk. (III,114)
So strong a current of vitality coursed through my veins that no movement on my part could exhaust it; each step I took, after touching a paving-stone of the square, rebounded off it. I seemed to have the wings of Mercury growing on my heels. One of the fountains was filled with a ruddy glow, while in the other the moonlight had already begun to turn the water opalescent. Between them were children at play, uttering shrill cries, wheeling in circles, obeying some necessity of the hour, like swifts or bats. (III,120)