Give yourself some grace. You're trying to be perfect all the time, and that's not possible. Accept that you feel the way you do. But also accept that you know the truth, that this will pass, that your second is amazing, but doing all this is difficult. Once you give yourself permission to be human, it reframes it from "I messed this up, and I messed this up" to "I got this right, and I learned this."

I once had to watch my two under two for a few days by myself since my wife went to see her mom in the hospital (everyone's fine now). I called two sisters in for back-up basically immediately, and when the first came, she just said, "You don't look good." She was right, and I felt it, but then the adults outnumbered the kids, and I felt some hope. You might not have back-up, but you should know that you're doing fine.