Not a problem at all. It takes time to develop that feel so you know exactly how much pressure you have on the bit and if it is too much or not enough. Quiet hands are the most important thing, make sure you aren't bumping the horse in the mouth, keep your shoulders and elbows fluid so that when you feel the pressure building in your fingertips, you can immediately reach out to loosen the pressure. I don't know how everyone else holds their reins, but I have found that it is easier for me to be soft when I have my reins closer to my fingertips, just about right on that middle joint of your fingers, and have them in kind-of a firm but relaxed grip rather than have my hand in a fist around them. Other than that, just stay aware of everything the reins are doing in your hands and the horse is doing with his head. Focus on trying to use as little force as necessary on the reins to get the response and use escalating pressure. Tons and tons of practice and keeping it always in the back of your mind are the best way. Of course, it doesn't hurt to have someone there like an instructor or a very knowledgeable person to correct you when you tighten up and don't realize it.