depends on what it is that your trying to improve at. however, the saying "practice smarter, not harder" usually applies.
"smarter not harder" means don't always practice something by doing it the same way each time. you don't get better by repeating the same actions over again if those actions aren't giving you the result that you want. all that does is make you frustrated and make it harder to improve because you're just ingraining a poor technique into your head.
what you need to do is try different variations in what you're doing to practice. in this way you will explore more possible ways that will help you improve whatever it is you're doing.
i remember reading an article years ago about a psychologist who studied practicing, and one of his subjects he was training to remember long strings of numbers. i tried to find it again, but i had no luck unfortunately, but it was really fascinating. basically his test subject would hit a wall where he couldn't memorize any more numbers, but then he would start grouping up the numbers into different blocks a block of 4 numbers, then 3, then 4 again. each time he hit a wall and couldn't remember any more, he would change up the variation of blocks, so 5, then 4 or something like that. after several months he was able to recall huge strings of random numbers that were read out to him. i wish i could find it again for you.