I'll be honest & say that if you're already a bit anxious having a third may not be a great idea.
The only reason I say this is that I was anxious when my first was born, used to worry a lot about cot death etc - really horrible thoughts.
Second was born & the worrying changed to awful senarios where you have to choose which one to save in an accident etc - became very stressful but tried to think well I have two hands I could grab both to escape etc.
These feelings went quite quickly but I remember the feeling clearly. I didn't really mention any of this to anyone.
When my third was born I had nightmares. Lots of nightmares! Car-jacking & trying to protect 3 young children, escaping a house fire & drowning. I did talk to family about these nightmares & also talked through strategies to protect all 3 which helped.
I know most people don't go through these thoughts but if you already sometimes have distressing/dark thoughts then consider it very carefully before having a third.
Mine are 9,8 & 6 now & I still get anxious at times but no way near as bad as before.
Having another one may just add a whole new dimension of anxiety!