One of the things I'm terrible at is improvising. I'm not saying I don't do it---I improvise all the time in cooking, and sometimes it ends up being a disaster. Especially when I'm cooking, I substitute, replace, adjust amounts--you name it, I change it. Then I'm either thrilled or disappointed with the outcome, and generally left with a mess.
It works with wellness too---make a plan, then when it rains on your running plans or traffic prevents you from going to spinning class----improvise! Do something else. It might be a blast, and it might not be exactly what you wanted...but it will almost always be worth it. If it wasn't worth it, you'll just improvise differently the next time.