lost ones marbles (verb) lose one's mind: go crazy
Sinonime: accomplished,
adept, battle-scarred, been around, been there,
competent,
expert,
familiar, hardened, instructed,
knowledgeable, matured, old hand, practiced,
prepared,
pro,
professional,
qualified,
skillful,
tested, toughened, trained,
tried, vet,
veteran, weathered, wise, worldly, worldly wise