I Am On Naproxen For Arthritis I Don't Take It

I am on Naproxen for arthritis I don't take it on a regular basis even though I am prescribed it twice a day.I try to take it once a day but not every day I manage. MY legs are stiff,and when I climb hills they see to get very weak after awhile Is this my own fault and do you think I would benefit more by taking twice a day