The majority of people I come across find themselves challenged by change. In the world of horses this is often when we find ourselves with a new horse that we don't know or when we move yards. Everything feels and looks strange and unfamiliar and yet we still expect ourselves to carry on as normal.
My recommendation is to slow things down, give yourself time to adjust and familiarise yourself with your new surroundings or horse. Your horse will be going through the same challenges as you and it only seems fair to give him/her time too. Imagine suddenly being moved away from your friends and routines to be plunged into a new and strange place with different sights, sounds and smells, with no friends and it wasn't even your choice! Wouldn't you feel a little upset? Patience and understanding is key, for both yourself and your horse.
Some horses can appear just fine immediately after a move which is great and then problems can start to arise after a few weeks. I believe this is because, like people, horses can become introverted when they are worried or they are simply in shock with their new surroundings and switch on to auto pilot. If this happens to you then know it will pass, it may well be challenging but it doesn’t mean the behaviour will last forever. The key thing is to remain consistent in what you are doing and be patient (my own biggest challenge).
Likewise, getting a new horse is a bit like marrying someone after one, short date (two if you’ve been thorough). We often don’t show our true colours until we feel comfortable with our partner so see your horse’s ‘self-expression’ as a form of flattery, he/she knows you well enough to show you how he/she feels. It is also your time to establish your leadership and I would always do this by playing with my horse on the ground (there are plenty of YouTube videos to give you ideas).
Take time to get to know your new horse or yard and set yourself small, yet achievable challenges. It's ok to take the first few days (maybe even weeks) off and maybe just groom or hang out together, what's the rush? Spending time on the ground together will help build a bond and trust. It will give both you and your horse space to settle and start to think more clearly.
Change is bound to challenge you which means it will ultimately change you, let that be for the better.