The song is about parting - could be interpreted as the parting of lovers or the death of someone close to you. 'I could never go with you, no matter how I wanted to' could refer to perhaps an illicit affair that has to end because one person cannot give up what they have, or alternatively to somone dying and the other being left behind.
'Run your hand along my gut, one last time' I think could hint at the fact that the person feels hurt or maybe has been hurt by their lover but rather than walk away this person would prefer to stay with their lover and be hurt rather than be without them. The horse is a metaphor for a woman/ person but of course itself has connotations of beauty, strength, intelligence and of something wild that cannot be tamed.
Hope this helps xxx