Zizou makes some good points. OK, so we can all come out with replies that "If you rode well enough you won't fall off, so learn to ride etc etc"
I had a bad fall a couple of years back. It knocked my confidence so badly it took me months to trust myself on a loose rocky descent. Even then I would stutter down it gingerly, which we all know is counterproductive. I just got myself back into riding something like when I binned it, big style, on a steep downhill riding over loose hardcore, and stuffed a brick end into the tender spot just under my kneecap.
I was on the point of giving up completely and selling the bike, but my son lent me his Kyle Straits and dragged me to a local quarry. Within half an hour I had plucked up enough courage to do a couple of chutes, and by the end of the week I was able to be a bit braver.
Now, whenever we go to a trail centre, I'll pack some pads, and wear them in the skills park to get a bit bigger/faster etc. On certain trails I wouldn't ride without them, as the confidence they give me is the difference between getting off and carrying the bike, or riding a tough section.
If the OP needs that boost of confidence, then a cheapish lightweight pair of kneepads may well be the answer.