What was interesting to me was, climbing with a new belayer, how difficult it was to fully concentrate on the climbing as I hadnt yet developed that trust in my belayer, not helped by when I glanced down, seeing him chatting with his neighbour!
I often see this happen, and the climber begins to shout down to the belayer more and more anxiously. This is a strategy which is guaranteed to create tension and actually make things worse. If you start shouting down (as you need to to be heard often), you start to over breathe and store tension in your body, creating an anxious feeling even if there wasnt one there beforehand. Also, it can create a difficult atmosphere - you may feel self conscious about shouting, your belayer may feel annoyed or embarrassed ("of course I'm watching you!"), and at this point, reassurance isnt usually going to help anyway.
A better tactic is to think whilst you are on the ground, do I trust my belayer? And if not, why not? Is it you (you never trust anyone's belaying!) or them (they are a bit sloppy). Either way, have a conversation about it with them, and work out what you both need to do to build that trust so you can focus on the climbing. Maybe its a bit of practice falling, maybe its a one off reminder that this is going to be a hard route for you, maybe they need to give you a bit of encouragement. Whatever it is, work this out on some routes you feel comfortable with before gradually trying something harder, so you can focus on the climbing.