I am truly happy and feel really blessed. It's a state of mind!
I consider myself really lucky, though other people often comment on how tough I've had it (not the best childhood, mum with severe mental health issues, my dad died in his 40s, sister also has mental health issues, premature baby, traumatic birth, husband had a near death experience where 30 of his colleagues were killed, he suffered from PTSD and didn't work for 2 years, marriage almost collapsed).
I'm easily pleased, not the envious/jealous type and try to see the funny side of everything. If things get really bad I remind myself that 'This too shall pass'.
On the other hand, my MIL lives from one bleak event to the other, refusing to see joy in anything, wallowing in self-pity.
I always tell myself that there's always someone worse off than me and to count my blessings. Also, I have really supportive positive friends! I don't see them often, but they'd be there in a flash of I needed them.