To remain happy for 24 hours is not possible because happiness is subject to physicality. Why do you want to be happy all the time? Imagine you have a happy smiley face showing all your teeth for 24 hours. You don’t want that right, even if it is possible?
However, it is possible to remain pain-free for 24 hours. When you become empty, there is neither happiness nor suffering. There is nothing. And that is the whole purpose of life — to be nothing.
To be in such pain-free state, you must find that empty space within you. You must identify the ‘Shiva’ that is residing within you. Look at Nova’s face above, it is the Shiva that is gazing, in nothingness.
For this, you need little effort. You need to start living life consciously. You need to do some Sadhana. You need to practice some form of yoga. But once you taste that space, you want to go back there again and again. You will find that material happiness is too boring compared to this.