I was friends with a very good nanny when DC were small and she gave me advice which I used.
Have something planned every day that gets you out of the house: can be playgroup, church creche, music group, baby yoga or swimming. Go out a second time each day to run errands or go to the park. Don't get housebound. Be in the world.
Hang out with other mums. They don't have to be your new best friends, but socialise. They can swap tips on weaning/sleeping etc. Go to or hold coffee mornings, invite them over for tea with their DC. Go for lunch together with DC or for picnics in the park. You have so much in common at that stage.
Make sure you speak with at least one other adult every day - a proper grown up conversation.
Go out once a week at least with your partner and don't talk about DC. Instead, do something together - go to a comedy or improv night, to the cinema or theatre or to a gig. Have a fun shared experience that doesn't involve being comatose with tiredness in a pizza place discussing the baby! 
Phase in plans for getting back to work. Look at nurseries. Do online courses. Meet up with old colleagues for a drink occasionally.
Allow yourself a bit of time off each week to get in shape. And do physical stuff with DC - get fit again. Run around the park with them.