Develop, practice, and hone this skill in low-consequence environments. That is to say, you should consistently be purposefully trying to perform trackstands on a regular basis in such a way as to minimize the risk of falling and getting injured. For example, riding to your neighborhood park with your children, going to an empty parking lot or garage to practice, or pedaling around a trailhead area while your riding buddy is still airing up their tires and prepping their bike/gear to ride.

Actively look for for windows of opportunity to spend a moment learning each of the levels of trackstanding while going about normal riding activities. Additionally, take time out of your week periodically to grab your bike - go find a calm area with inclines, vertical wall surfaces, and curbs - and just spend a half hour or so practicing trackstands without any pressure from others.