My idea is to keep the legs under the hips at all times when possible. This sounds simple but consider your walking and note if you are throwing one leg forward and than falling on it with your entire mass? Do you step away from danger using one step and form a sort of triangle which tenses you up?
Try for a while to walk this way: When you wish to move you relax your hips and move one of them toward your destination and relax the leg so it whips (in walking speed, this is not a hit although it can become one) and follows the advance of your entire aligned body. the other leg follows suit and hovers above the ground under your hips and is much more free to advance than if you plant both feet each time. This planting becomes rigid and tense after a short while and it is more difficult to transfer tension from the body to the legs and to receive hits this way. If when you walk you simply shift the support from one leg to the other you will also be able to shift the support when you are hit and be able to avoid tensed up contact it the legs (consider being hit in the leg when it is hovering relaxed in the air and when you stand firmly on it and try it with a stick by yourself or with a partner using fists and feet.) You will be able to slide this tension off you and another benefit will be that if you are walking underground or in dense vegetation your legs will be relaxed an thus more aware so you will not snag and get caught in wires and shrubs.
If you need an image to make this more real in your head before you try think about an ice skater like Vladimir Vasiliev writes in his wonderful book The Systema guidebook. Start out slowly and just keep your legs under your hips and play with the mass shifting with the hips and after a while your hips will relax more and than the spine will also be more clean of tension and free to move.