I used to think about it alot too - any sharp object, high places, walking out in front of buses, meds etc. it improved alot with my meds but I think the biggest thing was changing how I think about myself. Understanding that I am lovable and worthwhile because God loves me was really important to change the way I saw myself. Also that he created me so who am I to destroy myself? These two things helped me curb those thoughts and impulses. I still get the odd thought but I don't want to act on it and it is easily dismissed.