My mare is similar... She can get worked up when road riding, trail riding, hunting etc, although I've never had your issue of napping. It used to be worse when we were newer partners, it has reduced over time, so I do agree with those comments that suggest trust and time are big elements of your issue. Working my horse harder just made it worse. The only success I've had is time getting to trust each other and aiming for "little victories": walking just a few metres down the road without stress, keeping our trail rides to a walk so as not to encourage high energy, putting myself between her and objects that are causing stress, etc. Redirecting her energy when she is stressed or excited, instead of trying to block it, has been the most successful tactic in the 4 years we've been together. It has taken years to build up our trust, and unfortunately it's no quick fix as far as I've experienced! My personal situation was probably 1.5 years or so of being partnered before we really solidly trusted each other. There are still situations where she won't settle no matter what and I just have to deal with it until the ride is done, but as long as nobody's safety is at risk I'm willing to put up with it. My view of your situation is that you'll need lots of time to build trust if you decide to keep her and work it out. If that's not what you want (and there's no shame in that!), find her a home and move forward knowing you have a little more experience under your belt.