If it is primarily the mother who is hanging on to it at night, then the mother should make sure she gets plenty of sleep and rest during the day.
Rule out that baby is waking up because; baby is snoring (cold), if there are health reasons, or if there are problems with breastfeeding, reflux, stomach problems after starting solid food, allergies or other reasons.
Make sure to have the baby in the same room, as this can reduce the need for you to get out of bed. The mother can optionally let the baby sleep next to her in bed. The partner can optionally sleep in another room for a period of time, so that one partner gets to sleep and can have the extra energy during the day.
Make sure to get into a good putting routine.
Make sure to get outside during the day. It can be good to go for a long walk with the stroller.
Make sure to eat a healthy and varied diet.
Sometimes it can help to change the nap times a little during the day, or to put baby to bed a little later at night.
If you have a partner, your partner can occasionally take over. So that you can have a nice long nap, preferably for a few hours.
It may also be possible for your partner to take your baby in the morning, so you can get some sleep.
If it is difficult for your baby to be put to sleep later, you can let him have a late night nap. After the night nap, you can let your baby come out on the floor for a bit, or play and move around, depending on his age. Then, after a few hours, you can put your baby to sleep again. Here you don't have to go through the putting routine again.