We’re constantly making adjustments in our life, and our body goes through changes, transition periods, in which it’s bended — call it stressed, so it can develop new habits.
When you travel from one continent or time zone to a very different one, your body clock needs to adjust. It might take several days, if not weeks, but it will be just fine in the end. Changes are necessary, as much as adapting to them is essential to survive and thrive.