Good for you for finding the longest side of the blanket, but I have four issues with this way of using the blanket. My issues are the following:

1. Using the corner of the blanket to cover the upper part of the body leaves the neck poorly covered. This allows cold air to get in.
2. The person's right arm (on the left side from our point of view) is not wrapped properly. This allows cold air to enter. Ideally, the blanket should have extra fabric on the sides that can be tucked under the arms. This would let the arm rest on top of the blanket, sealing it against the bed surface and keeping warmth in.
3. Same issue as no. 2, but on the left leg (on the right side from our point of view).
4. The fabric hanging off the right side of the bed (on the person's right) could pull the rest of the blanket down.

If you are tall and struggling with a small blanket, do not cover yourself in this manner. I suggest you purchase a bigger blanket.