You can, however, reduce all types of pick-up. These can affect circuits in many ways. They often seem random, but there is always an underlying cause. If two traces are too close, current can flow directly between them. Two circuits that share a common ground or power supply line can influence each other through the impedance of the line they share.
Thermal effects can generate spurious voltages.
Nodes are most sensitive to noise currents if they have a high impedance and carry low level or very accurate signals. An electric field may induce the problem current, or it may come from circuitry connected directly to the node. Because trace impedance rises with frequency, this problem is worst at high frequencies. To disturb a low impedance point, a noise source would have to inject a large amount of current. Loops are sensitive to magnetic fields if they have a low impedance and a large area.