necessary to make a whole complete; essential or fundamental.
essential, fundamental, basic, intrinsic, inherent, constitutive, innate, structural
(of a person or action) creating or controlling a situation rather than just responding to it after it has happened.
enterprising, take-charge, energetic, driven, bold, dynamic, motivated
the state of being free from illness or injury.
good physical condition, healthiness, fitness, physical fitness, well-being, haleness, good trim, good shape, fine fettle, good kilter