You don't know what you don't know. Before doing B.O.C. flying I used to think how hard can a 6 hour flight signing on at 1 am "body clock" time be. It is a lot more taxing than it sounds to the un initiated, especially if you do them often, switching time zones, mixed in with other shifts in the same 28 day cylcle which are 180 degrees out of phase. None of this is taking into account noisy Hotel rest, very different to home or company rest area. No crew rest (short haul), list goes on. So yes i would say it is that difficult at times to get adequate rest before a shift.