How do I get my horse back in the stable?

[ayayayaya]

please help im losing FPs

[Sir Stardust]

Try going over to the Harvest Sprite Island, and hiring one of the Orange Harvest Sprites to work in your pet stable. Choose to have them 'Move.'
The next day, go into your stable, and ask the Sprite there to either move your animals out or bring them back in.

That's usually helped me in the past, after losing an animal/pet outside. ^^

[Ronin19]

You can get behind the horse and push while walking, not running. To walk, use the directional pad without pressing the B button or, with the stylus, make sure you don't go too far away from the character.