It can take up to 30 minutes for your eyes to get used to the low-light conditions in a tunnel when you are coming from a well-lit area. It is therefore advisable to reduce your speed to compensate for this. You should be cautious about using full-beam headlights when driving into a tunnel, ensuring you're not blinding other road users.

Keep in mind that the speed at which you feel in control of the situation is up to you; do not let other road users stress you into driving faster than you feel is safe. Their assessment of the risks is probably worse than yours.