If you have a problem with your horse, he starts acting differently than normal, here are some things to check:

• Get an equine dentist to check his teeth and do necessary work. Perhaps his wolf teeth have not been pulled, or teeth need floating.
  
  
• Check for ulcers.
  
  
• Get an equine chiropractor to check him out.
  
  
• Get his back muscles checked by someone who knows about saddle fitting. Check for kissing spines.
  
  
• Check his hocks.
  
  
• Get a knowledgeable farrier to check his feet for any problems, founder, crushed or contracted heels.
  
  
• Check for fleas, ticks, lice, ear mites, worms, etc.
  
  
• Check for worms; worm regularly.
  
  
• Sheath clean / clean teats. 
  
  
• Put him on low-sugar grass hay and supplement with B vitamins (be sure to get B1 in there).
  
  
• Forget riding for a while.
  
  
• Work on the relationship between horse and owner.
  
  
• Make working with a person beneficial to the horse.
  
  
• Start on groundwork; include some clicker training. Try the PNH 7 Games, Dorrance ground exercises, Lyons groundwork, TTEAM ground driving and obstacles, etc.
  
  
• When you're ready to prepare to start riding, be sure the saddle fits. Be extra extra sure! Either do the learning yourself or check with someone extremely knowledgeable about how to fit a saddle (not necessarily a trainer).
  
  
• If you aren't comfortable re-starting a horse in a sidepull, bosal, halter, or otherwise bitless, be sure the bit fits. Single jointed snaffles aren't always the best fit for Icelandic Horses because of the low palate and shorter length of palate (equating to less room in the mouth for the action of a single-jointed snaffle).
  
  
• Start in a small area. Practice stand for mounting, get on, get off. Build up your "basket of yes" answers (positive responses). The more positive responses, the better.
  
  
• Try not to rush or get ahead of yourself or the horse. Try not to get into situations or ask for something that you are not sure of getting a good response. Remember he may have lots of negative stuff to be over-written by positive stuff.
  
  
• Still in a confined area, work on walk, walk, walk, with head down. Long and low.