That is a very good question. Here's what someone on this forum said when I asked that same question a long time ago on this forum. The short answer is... raise your standards.
The long answer is that if you find three or four stocks trading at say.... a 20% discount to your estimate of value then you have this problem. So start looking for 50% discounts and discard the ones with a 20% discount. They are just not cheap enough. Bear in mind that Buffett never said value investing was about buying a dollar worth of value for 80 cents.
If you believe you are capable of correctly identifying a business trading at a 20% discount then it follows that you are also capable of correctly identifying a business trading at a 50% discount. In fact your chances of being wrong on the second count are lower. It is just more work. A LOT more work. Conversely, it is my opinion stock pickers who believe they can pick stocks trading at 20% discounts but have no idea what a stock trading at a 50% discount looks like are fooling themselves.
For what it's worth I probably sift through some 500 stocks to identify 50 trading at a 25% discount. It requires a few hours, perhaps a day or two for me to do that. Then I sift through 500 of those to find one or two trading at a 50% discount. That requires hundreds of hours.
Now if you have 3 or four ideas that you believe are trading at a discount of more than 50% let us know :-)