Laura, i am so sorry you are having to go through this at such an already emotionally draining time with your new bub. i am newly seperated too, however i am the one who decided to end things. Even though im the one who ended it, I still have huge sadness about the seperation and I still miss him terribly at times. i can't imagine the emotion you are feeling, but remember that you are not alone. it is east to feel all alone when your relationship breaks down.
It is a great thing that the kids father still wants a big part of their lives. Just remember that you giving up this time with your kids is a great thing for them in building thier relationship and bond with their dad, particularly cause of the split. Also, look at your child free time positively and start doing things for your self that you haven't done in 7 years. Meet up with childless friends, find a course or an excercise group to make new friends, read a book in peace, watch a whole movie without interruption, sit on the couch all day and not get up for anyone, lay in the bath and listen to the silence, catch up on sleep.
Try to spend as much time as you can around people who you know love you and will boost your self confidence and help you feel positive and happy. i spend lots of time with my sister and my mum and my friend cause I know they all love me unconditionally and they all boost my confidience and remind me that its not the end of the world and i can do this by myself.
Bookmarks