In part this is because the landscape is literally changing before our eyes. You only have to go to your local high street to see the closures and boarding over of shops that have been well established for years. For many individuals the changes are manifesting as a volvanic eruption as jobs go and relationships break up. For others it's more like feeling the tremours of an earthquake and feeling a certain nervousness about where to place one's next step as the ground could quite simply give way beneath your feet whilst those previously firm walls around you now appear to be no more secure than a house of cards.
Having gone through so many changes in my life, I now tend to be more anxious when things remain the same for a while! This does not mean I am complacent about change but I am able to distance myself to some extent. I feel that no matter what I have been through in the past, I did survive, somehow! In fact I often think I must be made of rubber as I seem to bounce back and just have to learn to live within a different environment. That of course is easier said than done. I know. Often it takes years to readjust and to gain a sure footing again.
The best way to gain that foothold is to only listen to positive people who have your best interests at heart. I don't mean those who jump in with advice thinking they know best when actually all they are doing is feeding you their own fears. I mean people who really listen, acknowledge your anxieties and can empathise with you. They don't necessarily have answers because the how and wherefore is different for everyone but they are able to support you through validating your experiences and giving you hope. This in itself opens your mind to new possibilites and thence to new experiences.
So next time you ask "What on earth am I doing here?" check with the people who really care about you not with those who are happy to bring you down!