Original Sentence that can/should be revised: If someone had worked with someone on something everyday, that person becomes stronger, Doodle worked on walking every day with the narrator and although it’s still hard he can.
Revised: Doodle worked on walking everyday, he got stronger because he was repetitively doing something.
Revised: Repetitively doing something builds up strength, for Doodle walking everyday made it easier, and his, usually straining heart, didn't have to work as hard.
Revised: For everyone practice makes perfect, when Doodle worked everyday on walking his heart got stronger and so did his legs.
Revised: Doodle worked on walking everyday, he got stronger because he was repetitively doing something.
Revised: Repetitively doing something builds up strength, for Doodle walking everyday made it easier, and his, usually straining heart, didn't have to work as hard.
Revised: For everyone practice makes perfect, when Doodle worked everyday on walking his heart got stronger and so did his legs.