hey jim,
welcome to the forum.
if you are able to throw the top to the ground and it is landing upright, all you have to do is work on is how much to pull back on the string before the top releases. it is almost the same motion as throwing the top down to the ground, just work on pulling straight back, in the opposite direction, and do it gently until you see how much effort it takes to get the top back to about where you hand is.
you don't have to pull back until the top is near the end of the string, it sounds like maybe you are pulling back too soon or too hard. what are you throwing? the heavier the top, the more effort it takes. on the lighter plastic tops, it's really a pretty gentle motion to get it to your hand.
good luck! keep practicing, it'll come to you.