Had a great horse, that showed all the signs all the signals... a young green untrained quarter horse gelding, gentle as can be. Showed all the signs. And then decided that the fall leaves were more interesting than join up. The fall back of an outdoor round pen! and it would be back breaking work to clear it. And then get rid of the grass. Now, I am sure with more experience on my part I could be successful anyway, but it hammered home the importance of learning and getting these experiences in way that sets yourself up for success. At first, one needs lots of practised with trained horses, in a preferably 'anti-septic' distraction free environment.
Once you've joined up 10s of thousands you can do it anywhere. But for those of us just starting... get it right!
That's always the problem without dedicated facilities, but then, not many of us do have them, so we just have to do the best we can with what we've got.
I have to work mine on grass, it is a distraction, but just have to go with it as no other choice.