Help me understand value investing

I've spent a large amount of time trying to understand value investing. I've read books like the intelligent investor, researched famous value investors and learned to find intrinsic value via dcf and other teqnuiques. The thing I still struggle with is the assumption that value is at all times relevant. By definition, buying a company below value means the market's pricing is inefficient. If it is inefficient now, how can you be sure that it will ever correct to intrinsic value. If I research a company to death and correctly determine that it's value is higher than market price, where is the guarantee that the market will ever agree with me and price it correctly? Curious to hear what methods are used to try and ensure a value investment ever actually generates profit.