This paper heart is called a Lucky Heart because it is made in the same way the Lucky Stars are made. Perhaps a name of Puff Heart might be appropriate since this heart is puffy and not flat. Model uses one strip of paper and requires cutting.
Cut a strip of paper. Almost any size will work, this one is 1" x 11". Valley fold the corner at a 45 degree angle to form a triangular flap.
Valley fold along the edge of the triangular flap.
Valley fold again along the edge of the triangular flap
Repeat wrapping the strip of paper around the triangular flap.
Stop when you have wrapped the paper around 5 to 7 times. Cut off the end leaving a section of paper that is about half the width of the triangle.
Make a small valley fold on the corner of the tail-end of the paper.
Tuck this section of paper under one of the existing layers of paper.
it will look like a tightly wrapped triangle.
Use sharp scissors to cut the corners of the triangle. Be careful, the paper is very thick.
Use your thumbnail or a hard sharp object to push a dent along the wide edge of the triangle.
Lucky Heart is done! They're so cute you might want to make a million more.
Size comparison. A one-inch strip of paper makes a heart that is a little bigger than one inch wide when measured from rounded-corner to rounded corner.
If your origami hearts are not puffing up nicely, then you are probably holding it the wrong way. The key is to hold the triangle along the edges when you push-in the wide-edge of the triangle. If you place your thumb ontop of the triangle's face, then your thumb will prevent the heart from puffing up.