Q:

How can I talk about my problems without having people exaggerate their gravity

Note: this is not a call for help or anything, I'm doing fine :)
I want to open up and talk about my problems, anxieties and depressive periods. The thing is, I'm used to it and it's often not as big a deal as people see them as.
Here's an analogy: imagine someone born with only one arm. When people meet them, the conversation can be something like this:

-Oh you lost your arm? That must be so hard!
-Well I was born with only one arm so I'm used to it, it's fine.
-But there must be so many you can't do! I would be devastated if I lost an arm.
-... 

People tend to compare it to how it would make them feel and not how I feel it.
Another example: sometimes when I'm sleep deprived I will sleep 5h a day during the week. People react very strongly to it, but I need 6h30, 5 hours will seem much worse to someone who need their full 8 hours.

The last thing I want is for people to worry and feel sorry for me. 

How do I open up without making people worry more than that should?
How can I be factual but make them understand how bad something is compared to my standards, not theirs? 

The fact that those people care about my well-being tends to accentuate that even more. Also, the more casual I am when I say things the more they seem to overevaluate how bad they are.
I had to put that note in the beginning because I didn't want you to exaggerate the gravity of my examples either ^^

A:

preface talking about your problems by talking about how things are normally for yourself.

I usually sleep 6.5 hours and that's enough for me to feel rested the next day but lately I've only been getting 5 hours of sleep and that missing hour and a half builds up.  

This way you begin with them thinking about how you normally manage and then introduce that you've been having a problem. By doing this you're not just placing a marker for where your problem is and leaving them to judge from where their perspective is but you also place your normal marker so the person you're talking to can measure between your markers and be less inclined to measure against themselves, if that makes sense.

