Unstable people are often very selfish. They look after their own self-preservation #1. My ex disappeared on me twice and he is extremely unstable, depressed and suicidal. It is something that I've come to understand.

Yes, it hurts (a lot) when they disappear and do a 180 turnaround on you, especially when you have tried to help them out. I helped my ex and he still disappeared on me and did a 180 as well. There's no getting around being upset by it and rightfully so. So I completely understand your sentiments and validate your feelings. In time, you will let this go and will move onto other things. You, too, have to look out for your own self. Best to move on and find someone who is more stable and reliable.