How much change can you stand?

Was thinking that I feel tired this week because of all the constant change in my life - and there is still more to experience. Are humans capable of living in a world of constant change? Where nothing is certain? For e.g had I not gotten a job, or a place to live, how long could I have coped? I understand people who venture to a different country and if they don't get work get depressed. I am very fortunate to have something in such a short time frame - 3 weeks is nothing really. Had that extended beyond 2 months then I would have been home. I know there is no point to wondering about things that didn't happen but these are more ponderings - when would enough have been enough. Not sure that we can exist in a world of uncertainty for too long a time.