Wooden gates get a lot of abuse from the weather. Hard soaking rains followed by a hot dry day can make the best wood gate curl up and misshape it’s self over time.
The most common problem with a wood gate is sagging. The heavy wood can really pull down on it’s self with time and drop low enough to start dragging as you open and close the gate. In the worst case the weight will warp the post supporting it and need to be replaced.
Most wood gate sagging can be eliminated with the use of a turnbuckle tension cable or rod. You attach one end of the turnbuckle cable to the top of the hinge side of the gate and the other to the lower outside. By increasing the tension on the cable it will pull the sagging gate up at the end and give the gate more support.