How to avoid the feeling of disassociation? I’ll randomly shut down and feel like disconnected.

What it sounds like you are talking about is a combination of long-term depressive symptoms and intense acute dissociative reactions to stressors. These are difficult things to combat. When we are depressed, especially for long periods of time, our coping skills erode as our depression deepens. As our depression deepens and the copings skills erode, our stress responses become poorer...do you see where this is headed...so then we begin to dissociate when stress occurs. Then when the whole cycle happens, we become anxious because these terrible things are happening in our lives...AGAIN! Does this sound even remotely familiar? If it does you might be caught in a cycle of anxiety, stressors and depression. This can be broken! It's not so much about how do you/will you avoid the feelings of disassociation, but more about how do you look at the whole picture and insert new coping strategies so that the whole system is supported so that the stressors aren't so intense so the mind doesn't feel the need to attempt to take the step back created by the dissociative process.

When is the last time you have taken a true deep breath? Don't brush it off. When is the last time you have taken a true deep breath. Try it. We don't remember to do it when we are stressed. The brain when stressed and depressed kind of goes into panic mode and will shut down sometimes when overloaded to super super super simplify a complicated process. I know it sounds way too simple to be true but deep breathing exercises can help calm the mind enough that you can take a step towards calming the anxiety enough that the body can calm down enough that the mind can take a break for a minute. I put it in that order for a reason. The breathing exercises will calm the activated adrenaline (fight/flight) system that is triggering the fear/stress response which is triggering enough anxiety to create dissociative feelings. Why don't we want to calm the activated thoughts that are driving the system? Well because if the adrenaline system is activated then it is in control. The breathing exercises will calm the body down long enough for it (adrenaline/instinct) to take a back seat and controlled breathing (thinking/non-instinct brain) to take control again. Then you can get back under control. 

Hope that helps some. 

Dr T