If you need to loosen a Britax harness, the first thing to do is find the straps that go around your child's shoulders and waist. Then, locate the two strap adjusters on either side of the harness. Push down on one of them until it clicks and then pull up gently on the shoulder or waist belt as needed until it feels comfortable for your child. Make sure to keep an eye out for any signs that your child may be uncomfortable in their seat, such as squirming or fussing. If they appear uncomfortable at any point during this process, stop immediately and make sure all straps are properly adjusted before continuing with travel plans. It is also important to remember to check the tightness of these straps periodically throughout trips; even if they were initially loosened correctly, over time they can become too tight again due to shifting or stretching of materials. Fortunately this process should only take a few minutes each time and could potentially save your little one from discomfort!