I've never cut myself or harmed myself in that regard, but I have dealt with a lot of suicidal ideations and was using drugs very recklessly with little to no regard for my own well-being. Taking a dangerous amount of drugs was somewhat exciting to me, like some people who binge drink take pride in how much alcohol they can consume, I took pride in how much drugs I could consume.
I'm diagnosed with PTSD, andI've had a couple psychotic episodes as well and was put on an anti-psychotic for a very short period of time but quit taking it. I have also been told I should consider going on anti-depressants as well, but am not willing to. I don't like the idea of using medications to manage my symptoms either, even if they are prescribed by a doctor. To me, it just seems to similar to my drug habits. I want to experience whatever emotion I have rather than attempt to mask or alter it with a substance, prescribed or not.
I find a holistic approach to be my preferred method to managing my emotions. The little things add up to make a big difference. I find that exercise is a necessary part of my daily routine in order to feel good. It is energizing and uplifting, plus I just feel accomplished and it gives me something to be proud about. On a similar note, diet is also important, although it doesn't seem to have as much of an immediate impact as exercise, eating healthy and nutritious meals at regularly spaced intervals helps me to feel energized, avoid feeling lethargic or weighed down, and promotes good health in general. Eating foods high in sugar/carbs can lead to spikes in emotions, not to mention lower self-esteem and lead to poor health. I still struggle with having good sleep habits(2am right now, wide awake) but sleep is important as well. I would suggest looking into healthy sleeping habits... I need to improve mine, it's hard to keep to a schedule or maintain healthy habits when your sleep is erratic.
Staying active is also a big part of mental and emotional well-being. If I allow myself to sit around all day and watch TV, it just sort of perpetuates a feeling of helplessness and depression. I feel much better when I spend time studying, working, and playing music. I try to set daily goals for myself based on what needs to be done that day. If I don't work or have school, I try to spend some time doing chores around the house. If nothing else, it creates a better living environment, takes your mind off of negative things, and gives you something to feel accomplished about.
I think one of the key parts of avoiding or preventing negative thoughts is to build self-esteem. When I just lay around all day watching TV or playing video games I start to feel negative about myself, feeling guilty and useless. That negativity tends to build and can spiral out of control. It tends to lead to negative behavior like drug use or self harm as well.
Live each day for a better tomorrow. Today may not be great, it might even suck. You may feel like shit and have no hope, but if you set goals(even simple ones) and spend each day trying to make your tomorrow better, over time things should improve.
This may all be a little oversimplified, and there are other things to consider as well, like stressors and environment, but I find that if I take care of myself and make caring for myself a priority, other tings come a little easier. Start with one thing at a time if you have to. Build slowly, it's not all or nothing. It's a bad day, not a bad life. Things can get better.
Your social environment is something to consider as well. Try to be around positive and supportive people while removing negative and demeaning people from your life as much as possible. I think it is better to be alone rather than be around someone who is always negative and demeaning. It's important to value and appreciate yourself. Try to regard and think about yourself in a similar way you would someone who you really care about. Be understanding and empathetic towards yourself. Don't beat yourself up, pick yourself up after you have fallen. Stand up for yourself, embrace yourself.
Talking to a counselor or therapist might help you deal with some of your emotional issues, but these are things you can start doing on your own that should at least help.
TL;DR:
I find a holistic approach to be effective. Daily habits should be considered. The little things will add up to amount to big things. Diet and exercise are important. Staying active and having positive outlets is important. Doing things that build self-esteem rather than diminish it is very important. Making a daily schedule that plans out your day by the hour can be helpful. I find my mood to drastically improve when I put proper amounts of attention to diet, exercise, work, school, music(constructive hobbies) and play(leisure time). For me, so much of staying health is balancing my daily routine.
Therapist or counselors can help resolve deeper emotional issues, but removing negative influences and replacing them with neutral or positive influences will go a long way.
Above all, care for yourself, appreciate yourself, and love yourself. Much easier said than done, but I find it is a more attainable goal if I reach my personal goals(on a daily basis even).