Scaling up trade size after initial success – how do you manage the psychological aspect?

I've been trading a small account for a few months, and actually doing pretty well, consistently profitable with my $ES and $NQ micro-futures trades. Now I'm looking at increasing my contract size, but I'm finding myself really hesitant to pull the trigger on trades I'd normally take without a second thought. It's like the moment the notional value gets higher, my brain freezes up. How do you all mentally prepare for scaling up, and what strategies do you use to overcome that fear of a bigger loss, even when your win rate is solid?