Well, we can't be happy if we have a migraine headache. We either have to wait for the headache to go away, or find some way to beat it.
There are many reasons why someone might have a dreadful life. We can't do much about fixing autism, for example, but we can address issues like poor impulse control.
First we have to take an inventory, and list on one side those problems we can't do much about, and on the other problems that we might be able to fix. It's been said that half the problems we have were created by ourselves. Digging into these self-created problems requires, first of all, owning them. This means we have to stop blaming other people, and this has to be done very early in the process.
All of this takes time, but what else are you doing?
Finally, happiness resists being grabbed. Pursuing it doesn't work. Letting it grow like a sunflower does.