When using Zettelkasten, or any other method or system of knowledge management and note taking, guard against confirmation bias.
Don’t arrive at a hypothesis and then look for facts, data or notes to support the conclusion. Look at the notes, make connections, look at disconfirming data and facts before arriving at a conclusion.
Disconfirming facts are valuable to help you to think about something from all points of perspective. The important thing is that the notes you add to your system are relevant.