Your glasses will feel very uncomfortable if your frames are too tight on your temples. On the other hand, if your frames are too loose, it can look and feel a little awkward.
Either way, you can adjust your frames at home for a more comfortable fit:
If the arms squeeze against your temples: For metal frames, use your nondominant hand to secure the lens of your glasses. With your dominant hand, apply very gentle outward pressure on the corner part of the frames located between the arm hinge and the lens. Repeat on the other side of your frames for a looser fit around your temples.
If the arms fit too loosely at your temples: Again, only for metal frames, use the same method used to loosen arms, except apply gentle inward pressure on the corner part of the frames located between the arm hinge and the lens. Repeat on the other side to tighten the fit around your temples.