Variance is a key concept to understand when value betting, especially for those who have previously used matched betting, and are used to guaranteeing profit.
It can be difficult for new to value bettors to understand that even if something is value and beats the closing line, it can still lose. There can even be periods where 10 bets lose in a row, or 10 bets win in a row. Over time, so long as you are taking value, the pattern will smooth out and it is a guarantee that you will profit. This is because your expected value is positive.
As shown on the chart below, your profits may vary from week to week and you could be in a loss for several weeks. But over time, so long as you keep taking positive expected value overall (meaning you're beating the closing line more often than not), your profits will gradually increase.
*Image Credit-Pinnacle