This is the role of the inner-Mother
Perhaps we were not taught good self-care habits or fight with ourselves about doing them.
How do we learn self-care rituals that are healthy & do them in a joyful balanced way?
Healthy motivation can be illusive,
but we need to heal the dis-connects with ourselves as well.
The same ideas apply here if not more.
When we have children this issue comes glaring back at us.
If we have any issues about self-care, it all comes up.
Do what you do out of love, not from fear and it gets easier & easier to do more regularly.
Listen to how we speak to ourselves... is it loving?  Are we phrasing things in an affirming way & re-directing ourselves to be better each day, or is there a lot of fear & unworthiness messages.
The inner-Mother nurtures us & teaches us to nurture ourselves in a healthy way.
Look to the relationship with our birth Mother (or the one who raised us) for clues as to why it gives us pain to do good things for ourselves.  Facing this pain & understanding & where it comes from, is the truest way to make peace with our own inner-Mother.