When you have the money to fuck up.

I definitely recommend it when you have back up, lol

When you’re sober.

Depends on the recipe, but in general I’d prefer to eat first.

For me I’m usually getting hungry by the time I’m cooking something new but I’m not cooking a new recipe because I was hungry. Let me explain.
I’m hungry -> I cook something like usual because I’m hungry now
Wheres: I have an idea/inspiration -> time passes -> go to the store for ingredients -> time passes until the next meal so I’m hungry again -> cook the new recipe

Yeah, sometimes it takes longer than expected and people get a bit too hungry, or sometimes you make a mistake and ruin the meal but oh well. The more you do it, the better you will be at anticipating errors and avoiding them. Especially if you also focus on the why not just the how when learning new techniques/recipes. Also, many recipes leave out some of the most important information, e.g.: mix the dough. It’ll probably say mix for X minutes. What is the expected consistency; does temperature matter - if so, why; am I trying to develop gluten here or avoid it? (baking is trickier for me, hence the example)
By understanding the why and not just blindly following the recipe you will achieve consistent results much faster than by trial and error.

I still try to avoid making something completely new to me when inviting guests, but otherwise all bets are off.