Caution Warning: Suicide

I've been struggling with suicide ideation kind of. I'm not thinking about it and I stop myself from exploring it but I've noticed over the past week that even though I'm suppressing these thoughts I still find myself absent mindly muttering "kill yourself" under my breath or scribbling "kill yourself" in my notebooks. I want this to stop and I distract myself and try to think of something else and it works for awhile but it keeps coming back. 

My therapist suggested it might just be out of habit now which means it shouldn't be too hard to break if I stick with it but I feel like I need to effectively squash it now. 

I would love tips on how to stop these real dark thoughts so I can start getting better at tackling the other negative but not as drastic thoughts I get.