for those who stay for long hours in front of a screen, chatting or surfing and who doesn't these days, RSI isn't fatal disease or injury don't take this article too serious it's not cancer we're talking about but it's really annoying and stressful and can go seriously bad. It could happen to anyone. With more tasks and jobs being done through computers, It will certainly happen to more people, and you need to act against it, if you care
So, What is RSI ?
According to Wiki
Repetitive strain injuries (RSIs) are "injuries of the
musculoskeletal and
nervous systems that may be caused by repetitive tasks, forceful exertions, vibrations, mechanical compression (pressing against hard surfaces), or sustained or awkward positions".
[1] RSI is also known as
cumulative trauma disorders,
repetitive stress injuries,
repetitive motion injuries or disorders,
musculoskeletal disorders, and
[occupational] overuse syndromes.
Cure
If your case is serious I advice you to visit a doctor directly, if you're in early phase just do the following and hopefully you'll be fine, If you didn't then you must go.
So first you need to Adjust Your Sitting
I can not insist more on this, I was the guy who would put the laptop on his lap, lay or sit on bed and all the postures you can think of, and that when my hands and rest started to hurt me, When it started to happen more frequently I was unable to code, I was literally going mad, I'm about to lose my job and maybe career, it can not be more serious than this, and I don't like going to doctors unless I have to, so I google and googled and everytime I read something new; first answers were adjust your sitting posture, I ignored it and started buying different ergonomic keyboards and
mice/mouses, I ended up with more than 9 keyboards and 10 or more mouses, I spent a fortune I bought different makes and from the lowest to highest, problem wasn't fixed until I figured out I just have to sit straight as the book said.
what are the secrets behind that perfect posture ?

- The chair
- Again The chair
- elbows free and 90 degrees with keyboard
- Screen height
- strong chair back
Change your habits
There's a say that brain can't concentrate more than 50 min on a specific subject and will often need a break, so have a break every 50 min for 10 minutes just try don't sit there for hours and have a walk along the place.
Mouse the source of trouble
If the mouse was the source of your pain then you're reading the right article because this was exactly my condition, Try to avoid any as they're the main cause of RSI, the alternatives are (Touchscreens, good touchpads, good keyboards, memorizing and printing Windows/linux/ Mac shortcuts. At the end of the article you'll find some tips if you need to use a mouse as a backup.
Internet surfing with only a keyboard
Use
Vimium it's an extension on Chrome it's just perfect, you press f and suddenly all the links on the page have alphabetic shortcuts of one or two alphabets it's just amazing and quick, try it and read the description over there I won't explain much.
Touchscreens
Whether it's a tablet or a touchscreen they're good choices but not always, sometimes you just need a mouse and keyboard for a desktop, either you're out of budget or you're at work.
Keyboards
I've tried many keyboards best ones for me as PC(linux/windows) user:
Generally speaking laptop keyboards are the best specially Dell Inspiron, any Mac, and most VAIO's are good. I have no idea why Desktop keyboards aren't similar to those, it's very rare to find a desktop keyboard that has the following properties:
Thickness: Short
Touch sony VAIO and Mac users will know what I mean, try to find the non slippery ones
Feel
Keys with long press aren't my favorite, you'll find them in normal Qwerty keyboards. My favorite are the ones where you feel a click when you press them.
I've found the perfect click one it was called
Microsoft Arc keyboard though the design was horrible the guy who made it made a
terrible mistake he made one Arrows key instead of four it looked like a game controller and in the casing you wouldn't see that pitfall it's like they realized it and covered it with an icon, but when you get the keyboard out and you have sense of detail you'll see it.
Design this is very important because when you're at the mall your eyes get blurry by different designs trust me Just stick to the design you're originally comfortable with, for me the best is the minimal with spaces between keys, (you can see that clearly in Macs keyboards)
Mouse
There is no way of avoiding a mouse, at the end of the day you'll need one just to use in case of anything, so just don't start using the quirky ones you find with strange and sometimes fancy design, your best bet is to stick to
Logitech those guys know what they're doing, specially in mouse designs. Also wireless mouse are the best not because they're just wireless no because the wire increases resistance against your moves which causes stress for your psychological state, and affects the muscles gradually, I'm no doctor but this is exactly what it feels like when switching between a wired and wireless mouse.
Note
I wish you and myself well and good quality of life. Though don't forget about those who can't afford anything of what we're talking about in here, we're certainly blessed (if you're believer) lucky (if your non believer) so when you buy good thing for yourself whether it's pricey or not, remember them and try to help.