Avoid the Sunk Cost Fallacy

This is true both literally and figuratively. In the former camp, you can make yourself extremely miserable by repeatedly trying to force equipment, outfits, or excursions because "we paid X for it." You have already spent that money. Insisting your hysterically shrieking progeny has to sit on a jolly red-suited stranger's lap means that you bought something stupid AND made everyone in earshot miserable. An important corollary to the "release early" adage is "bail early, bail often." 

Assuming you didn't decide to have children to celebrate winning the lottery, recovering money from scarce-used baby equipment is easier than ever. There are online marketplaces, local thrift shops, even verified resellers for pricier items like SNOO bassinets that allow you to recoup almost the entire purchase price. 

(Alternatively, there's always the priceless experience of taking a sledgehammer to a stroller that wronged you on a particularly fraught vacation.)

On the more figurative side, don't get too attached to The Plan. Your best intentions can and will blow up in your face with the spectacular hoopla of a toddler discovering an unsecured powdered sugar canister. You need to be able to pivot.

Schedule check-ins, book a therapist to help you with a mantra, but find a way to recognize when the path you're on is no longer serving you. Doing something the hard way longer than you need to is a waste of the little time you have.

Memorize the phrase, "Okay, I guess we're doing this now."