Take an advil beforehand. Your back and shoulders and hands and everything else will hurt. I use to do quite a bit of hand sewing, but it is tough on your body. I love my machine!
Zen out. Don't set deadlines or pressure yourself, and enjoy the activity for the calmness it can bring. Don't get pissed if you have to rip out some seams and re-sew, although I'll warn you that handstitching is hells harder to rip out than machine stitching. Wash/shrink and iron your fabric before you even cut it. Wash/shrink and iron your fabric before you even cut it. Wash/shrink and iron your fabric before you even cut it. Repeat this at least ten more times. No one starts out a pro. Start with simple, even meaningless things, as your skill improves you'll know what to tackle next. I started by hemming a couple of pairs of pants, last projects were a tailored 15th century doublet and an 18th century justacorps. Not bad for an all-thumbs 50-something guy, but I'm sure the next project will turn out even better.
buy a machine! just kidding! i admire people who have the patience to sew by hand. i could never do it, they just end up as sad, unfinished projects!
Lean up against a wall or a good tall chair so your back has support, it's the hunching over that kills ya. and nobody mentioned beeswax, you buy this little thing at the fabric store with a disc of beeswax in it, wax your thread before you sew and that'll keep it from gettin' tangled up. So don't forget to mind your beeswax
I always sew with some semi-involvement required movie or PBS show. My mom was a needlepoint to the TV kind of woman for years. (and i try to dance if I have music going and tangle the threads)
I did my best hand sewing sitting on the beach...at least until it's to cold then me fingys go numb...enjoy and make sure you stretch and flex your fingers and wrists cause repetitive actions can cause soreness as aforementioned and possibly carpel tunnel stretch stretch and you'll be fine...see if you learn ambedextriousness to ease the strain on one paw...have fun!
I'd suggest you start on small projects. Shortening a hemline, doll clothes, something you can finish in a day, so you don't burn out and never finish. That's how I learned to sew, and how I plan to teach my children to sew. Machine sewing is much easier if you've already mastered the required patience and other skills required to do it by hand. I find hand stitching to be very relaxing and meditative. I often do it in front of the tv or while listening to the radio.