Knitting requires a lot of fine muscle control and coordination, a lot of mental focus, patience and perseverance. Without them, you won't be able to finish any bigger work. Don't be afraid, if you're missing in one area or another. Maybe the US 15 needles are a little bulky for you.
You can try a 5mm or 6mm one. They're not so small that you have to hold them tight and not big enough to make you feel clumsy holding them. I recommend starting with bamboo needles because they are less slippery than steel needles. They have more surface strength, so stitches are less likely to fall off.
Very young children can also learn to knit. The exact age will depend on the child's manual dexterity and hand-eye coordination. Some may have the necessary skills at age five, while others may not develop them until they are around the age of ten. I just spent the last 6 hours' knitting 'with youtube tutorials in front of me, and I've literally done 0.
A little tip if knitting the first row is too tight: put two needles together, then pull out one of the needles and start knitting. When I started knitting, I tended to make my stitches too tight, especially the fused stitches. That said, there are a couple of common and easily avoidable mistakes that cause new weavers (and their teachers) to stumble. When slowing down, knitting is supposed to be relaxing, but sometimes I get anxious to want to finish or move on.
According to the Internet, I am discovering that the jersey is made alternating the backhand and the point and the garter is all point of point. I understand that you want to make sure it's a nice and even stitch, but you don't need to pull hard, the yarn you're wrapping this time is all the space you'll have to knit next time, so you'll need to be able to get your other needle into it. There's no real trick to this other than remembering to bring your yarn to the bottom of your work when you start knitting. It should be at least a couple of hours with minimal interruptions at first (although soon you should be able to knit and listen to a podcast or watch TV).
If you used a loopback throw (also called “easy to throw” in one of the how to knit videos), then that's pretty normal. Everyone has problems with their knitting from time to time, but most of the time it's easy to correct knitting errors. Try both and you'll probably find that you prefer knitting for certain types of projects and crocheting for others. Doing so will result in a drooping stitch, which looks like a big bow (a stitch, essentially) that will simply hang on the side of your fabric and eventually fray.
Still, when I hear that last answer, I try not to talk over and over again about how soothing and anchoring tissue is, nor do I throw statistics on how sewing has been shown to reduce stress hormones, or how it can help eliminate addiction, and even potentially prevent low-level memory loss. There are a lot of variables to consider when trying to figure out which craft uses the most yarn, knit, or crochet.