I strongly recommend the Wonder Weeks. You don’t really need to read every word. Just understand that your baby will go through big developmental leaps, and that those leaps will first make them fussy/scared -but later make them a genuine joy to be around. If you go into it expecting that kind of pattern (and able to recognize when you’re in a fussy phase), you’ll do great because you won’t over-correct to a 4-day fussy phase. It also just lends some sanity when everything that used to work suddenly doesn’t anymore 🤪