Have you ever noticed that the best hitters in baseball have an incredibly smooth swing? They don't "swing for the fences" - that's what hitters with a high strike out number have. They have a sweet, smooth swing, that connects the sweet spot of the bat to the incoming ball and the ball flies off the bat with incredible power and precise direction. Having a light touch when playing your banjo or any instrument is essential in sounding your best as well.
Playing with a light touch pertains to both of your hands. Tension in one hand travels through your entire body and effects both of your hands, arms, and even your ears. Let's assume you are a right handed player. When you strike the strings hard with your right hand, you tighten up all over your body and this inhibits your ability to play smoothly and quickly. By keeping a light touch, you can stay loose, and your muscles will move much more effortlessly - thus allowing you to nail those licks that have been giving you a hard time, and allowing you to concentrate on tones, rhythm, and what others are playing (when playing in a group situation).
When you strike the strings with a light touch, you also have room for dynamics. Dynamics are one of the easiest and most effective ways to add personality to your music, yet - they are one of the most underutilized. If you always play very hard, there is no room for movement up.
When fretting the strings, you don't have to choke the neck of your banjo or push the strings all of the way down to the fingerboard. You only need the the strings to be pushed down enough for them to make solid contact with the fret in front of them. Many people fret their banjos too hard and wonder why it hurts their finger so much and they still can't get a clear tone.
One of the most important parts of consistently playing with a light touch is to breathe. Often players will, without knowing it, hold their breath while they try to play a difficult lick. Once you do this, the entire body tightens up. So really concentrate when practicing on keeping a smooth and relaxed breathing pattern.
Try playing some right hand patterns focusing on your touch. Listen to get the best possible tone out of your instrument. Try to play with the least amount of force while getting the full volume and best tone out of the banjo.
The best players generally always have a very light touch. Look at hitters such as Hank Aaron, Ted Williams, or Micky Mantle - they have beautiful, smooth swings. Banjoists such as Bela Fleck and Jens Kruger make it looks effortless for them to play the incredible passages they play. These players also have incredible tone, rhythm, and note choices. All of which is heavily helped by their light touch on the banjo.