I think it is good to keep practicing but if after several shots you are falling off then your form must be affected by the strain of holding as you get tired. Going from 67 to 63 isn't that much of a drop and I would lower the poundage and re sight the bow and practice until you can shoot the same shot after shot within reason. Then you can slowly up the poundage. Remember that shooting at a target in summer weather is different than sitting for several hours in a tree stand and then having to take 1 shot when you are cold, cramped from non movement and need to get the shot right. Less poundage is usually better for this to happen as planned. Once I practiced almost all summer and when the shot opportunity came I was real cold and had to crouch to shoot under a limb. I had a real difficult time pulling the bow back and the next day I lowered my poundage by 5 pounds and re sighted the bow. For the record...I missed