You will have the "Simulate Paper & Ink" option ticked. For generic screen profiles, such as sRGB, AdobeRGB and ProPhotoRGB, the three main one, although there are more, this is not an option. For printer profiles it is there to simulate the difference between viewing a reflected light image, as you get from a print, and a transmissive light projection system such as you get with a monitor or when using slide film. Actually unless you are using an old CRT, looking at a monitor is just like looking at a projected slide. You have a white light source that you view through a coloured filter. Anyway under most normal viewing conditions for a print it will generally seem a little less saturated and contrasty thanks to the fact that you are losing some light in the process of it being reflected.
I usually find that having the Simulate Paper & Ink selected matches my prints a little better than not selecting it. It also depends on how they will be presented. I usually find that when framed under glass and hung on the wall you lose a bit more than viewing under controlled circumstances in a good viewing environment. If you are finding that your prints look more like the sRGB proof then untick the option and you will see a significant increase in the brightness and contrast. Try that and see what you think.
I do not know about the lab you are using, most will want you to submit in sRGB and will handle the colour for you. I use a lab here in the UK that is quite unusual in that it offers an alternative to the usual types of upload systems (Often that is a system called ROES) that allows you to make choices in cropping for aspect ratio and other tweaks, these systems usually require sRGB, or will convert to sRGB first for the online editing stage. In this situation it is important to export in sRGB from LR and not to use the printer profile. I know of only two or three labs in the world where you should submit in anything other than sRGB. If you create a proof copy in LR you should remember that the proof copy colourspace will be used during export, not the colourspace set in the export dialogue. There is no warning of this.