I have noticed that some people have a hard time dealing with being unwatched.
But hey, don't let this get to you The more watchers you have, the more people there are to unwatch you. Some people decide to watch others, and if you are not the type to watch back - they might unwatch you just for that. Like I only watch about 30 deviants (groups included), though I don't know to what extent that affects my watch rates.
Of all the watchers you have, surely the time will come for some of them to lose interest in what you draw - perhaps they are no longer interested in for example Soul Eater. A huge amount of my watchers are (were) Tiger and Bunny fans. Now I'm spamming my gallery with Soul Eater (mainly Death the Kid) and I can't blame people for unwatching me if they are not interested in that.
I don't check out my watch rate that often but I experience some unwatching from time to time, at least a few times each month I'm guessing. And yes, it hurts. But there's no need to take it personal - I too unwatch people, even if they make awesome art – and I’m not doing it make the other feel bad. I just lose interest for whatever reason.
Also having many watchers doesn't always say that people pay particular attention to your work - for example I'm supposed to have about 240 watchers but I barely notice their "presence".
Whenever I upload something, only a few give feedback - which is about 7 people. The other 200 plus watchers? Some people silently look at it or give it a fave, but I think the majority (70%?) just skips my stuff or ignores it. People that tend to watch many deviants have a whole pile of work to go through in their mail everyday. Like people who watch hundreds of deviants - I won't be surprised if they accidentaly - or on purpose skip my work. Having a mailbox with hundreds of deviations gets tiring. Your single deviation would have to compete with all other deviations in your watchers box and if it doesn't stand out, that's too bad.
Keep in mind that it's also likely that some of your watchers aren't as active on Deviantart anymore.
Some watchers might have lost interest in my work long ago, but forget to unwatch me because I don't upload stuff very often.
I don't know what my watchers think of my stuff - that's why I love to receive comments a lot more than receiving watchers or faves.
It sure is nice having an audience for your work. Though in my case it made me hesitant in uploading stuff I like. Like the Black Star x Kid which has become my otp = how many people actually appreciate that? I can count them on one hand. The Soul Eater fandom is the straightest fandom I have ever been in so I feel like a turkey in a crowd of chickens. I can totally see myself losing watchers from drawing too much Deathstar. But I'll still continue to draw it, because I draw and upload things on deviantart because I think it's fun and I like to contribute to some small fandoms that share a similar interest. If there is only one person who truly enjoys seeing my stuff, than that's what makes it worth to me to continue uploading stuff on deviantart.
Overall I don't think you should worry too much about watchers, because this is very subjective. Like my Naruto drawing I uploaded recently - it broke all of my viewed/faved/downloaded records in two days - in comparison to what it normally takes for my "not-Naruto" drawings to reach that count (one week to 2 years) and to be honest, it got me down quite a bit. Because it once proves that the succes of your drawing often depends on the series you draw. Because that Naruto drawing of mine sucked ass. I spend way more effort in some of my other drawings. So as long as it's Naruto it's okay? Damn. Though the same can be said about Soul Eater - it's easier to favorite something that people already know and love. Some people who draw original stuff that has no fanbase hardly have any watchers at all, no matter the quality of their art.
Don't worry about people unwatching you - it is no use having watchers that only pretend to like your work, or just watch you for the sake of being watched back - as much as it's no use having thousands of friends on facebook you hardly ever talk with.
Just keep drawing and have fun