Complex sentence: Snoopy then makes himself some dinner, Snoopy is still crying over being heartbroken from Fifi, then he realizes that the Circus is her life and his home is his life, then he retreats to his doghouse.
Split into simpler sentences: Snoopy then makes himself some dinner, still crying over being heartbroken from Fifi. Then he realizes that the circus is her life and his home is his life, and he retreats to his doghouse.