Well welcome to SoM first off. Secondly how long have you been trying to do this?
In my opinion, have you ever thought if you were sick? Because this has often happened to me when i am sick, which i am right now actually.
For me, sometimes too, if i am physically not ready to do any thing related to magic, or trying to calm myself, it just isn't meant to be at that moment.
Before grounding, or stuff like that i would suggest, having something along the following like :
*A warm but not hot bath, possibly with bubbles. Let your muscles become loose, and let your thoughts stray.
*A cup of tea. My favorite is Earl Grey (the specialty) and i often drink chi tea. I always do this, before ritual, and after. Or if i am just having difficulties.
*Dancing, or jumping around wildly. I know it sounds crazy, but if i have energy that i don't need, it sometimes disturbs me, when i try to work on meditation. So i usually dance, until i'm tired, which sucks because i don't get tired fast, since i dance.
Stretching is another form as well. Not only is it good for your muscles, it helps with arthritis, it also can make you more loose, and relaxed, but it can after i while also give you energy and a calm feeling, despite the pain when first starting out.
I don't have any other tips at the moment, but i hope one of these will help you at least. Hopefully this helped.