When you buy or lease or whatever a "new" horse - one that you are not familiar with - it takes approx. 10 HOURS (not 10 trips) for him and you to come to terms with each other and understand and respect each other.
For whatever reason, it seems to be the MAGIC NUMBER - 10 HOURS.
The little darling. is not used to your methods and you are not used to the methods that your NEW darling was trained with. So, it is going to be pretty darn confusing for the both of you - therefore, very frustrating to both.
So, you CANNOT allow yourself to be frustrated - patience and consistency are the BIG keys here. In 10 hours, the both of you will probably get to finally know and understand each other.
He/she needs time to learn how and what you are asking. He really doesn't have a clue and will probably act up in frustration and crappy behavior because he just plain doesn't understand. You need to just LET IT GO, and not get mad, and go about what it is that you are trying to accomplish, for example, whoa, stand, don't move when I mount, don't jig home, etc.
Neither one of you understand the other - it is as if you communicating in totally different languages or dialects.
Plus, don't forget he/she is also in a completely new and sttrange environment - away from his comfort zone and his buddies.
Be kind, be patient, be consistent, and put in the time. You can do 10 hours !