The greater the applied stress range, the shorter the life. –somewhere on wikipedia
Compile time (or lack of)
This an outstanding source of stress. When you burst out a big chunk of code, you guys hit F5 and see the result, right? Not working? Get back to work. Now.
Back-end developers can always rely on compile time (or more contemporarily, build time) to relax a bit. They can soothingly peek at their EVE online character skill training queue, answer a couple of tweets, or practice their vi kung fu.
Source code management
In my experience, front-end devs aren’t at ease with SCM (subversion, Git, etc). That means when there’s a fire, a hard drive failure or a giant dinosaur spits fire on your laptop, you lose everything. Sure, there’s a copy on the server, but that’s not how you do things (and what if the dinosaur also ate the server?). Lots of time lost here, lots of stress.
Web standards are a good thing. But web standards, as they are advertised right now, are a real joke: you still rely on browser maker’s willingness on implementing them. You still have a lot of tweaks, hacks, and duplicated code to craft.
Standards for back-end programming (JEE, SOAP, SQL, to name a few) are well defined, and mandatory. The developer can lean on them and blame the product company which failed to implement them correctly (and get congratulated for it because you earned your company free support time).
Have you ever tried calling Microsoft, and open a support ticket for that unsupported CSS thing in IE?
Even the worst snippet of C++ code, if it works, isn’t judged by anyone. Why? Nobody understands it. Nobody gets to see the actual code, it’s all 1s and 0s.
On the other hand, you front-end guys have to deal with the judging eyes of everyone in the company. You have to take all the “Meh. I still don’t like that turquoise” … even if it ‘s the best darn piece of code you ever wrote! You literarily get stripped of all your intrinsic self-worth.
What if you were in a crowd (a big one, think Tahrir square), and someone removed all your clothes. Nobody would like that, unless you’re sexually deviant. That’s what happens when some guy does a right-click -> view source on your code. Guilt, doubt, fear.
I fear for you guys. Really. I could suggest a couple of COBOL books, or Java certification classes, but if you already have a couple of years of experience behind you, I guess it’s a little bit too late. What might help is if you try yoga, tai-chi, or as a last resort you could try the essential works of Yanni.