Never leave your knife in humid conditions and certainly never put it in a dishwasher.
Apart from giving an exceptional cut, the carbon steel has a tendency to rust. Always clean the blade well with an oily cloth after use, greasing the knife and the joint often.
A sharpening blade or grinding stone can maintain the cutting edge of the blade. In order to do this, run the stone along the blade from the base to the tip at an angle of 20°.
A "sharp edge" is formed on the cutting edge opposite. Remove it by running the stone on this side but without exerting any pressure.