Hi there, I am so sorry to hear you’re struggling, it’s an absolute horrible disorder to try and manage especially by yourself ( fellow bpd person ) . I did find what you’d call demonic easier to contact with results ( angels have a quite a high vibration so it’s more subtle? Not that they’re not willing or trying to help ) when we’re low / depressed our vibrations are lower, more dense. I feel like the demonic are closer to our vibrational level not that they’re what we’d deem negative, just more on our “level” regarding being able to feel their presence with quicker results. Honestly it’s what or who you feel more comfortable with and who you click / connect with 
good luck, feel better soon.
I have a cousin with BPD and a few close friends (all being female except for one). They’re emotionally intense beings that you really can’t be around for long, unless you have the patience and effort for it. Fun and warm-hearted beings nonetheless who often carry great looks and charms with them.
I can imagine with the amount of intensity they’d constantly be feeling would work great for fuel in magic and could perhaps patch up vulnerabilities in the personality once working with an entity.
As far as generalisation goes, I’d say 40% of treatment successes is appointed to therapy and medication when required, the other 60% is your actual lifestyle. Diet, sleep-patterns, daily habits and activities etc etc. So because you don’t have DBT in your country, it does not mean you’re at a disadvantage. The doctors can only take you to that 40%. You have more than half to amount to still.
I think a lot of people resort to magick because of a fragile state of mind just for the sake of ridding it. So in saying that I literally have no qualms in saying that you could speak to any practicing magician or occultist and they themselves have probably also been through some devastating and bad shit (mental illness, traumas, dark emotions) in their life.
What makes me appreciative of them is that they’re more concerned on tackling the problem or making observations than deducting your actions and behaviour as a poor judge of character…They will judge less than others.
They’re generally a lot more accepting of people and their ways because they understand as they’ve been to those depths. This forum like others have mentioned is kinda like that. Very open and smooth to just say what you want and it could be something that means a lot and someone on this forum understands. 
To answer your question, yes you can use magick with a fragile state of mind. Work with a deity that will bring self love and care. Do not do anything daft like a curse spell out of spite of the moment.
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