Is it better if you leave?

My partner and I have been together for 15 years and the last five have been extremely hard.  I have contemplated leaving many times.  I hate how I feel around him.  There is very little effort, little sharing of partnership, a lot of similarities to what I have been reading on this site.  What I would like to know, is it better for those who have left?  Is it better for you mentally?  Better for your children?  I so want to do the right thing and I do love my partner but his ADHD is destroying me and I don't know how long I can continue to endure it.  Can anyone speak to leaving and how they are doing?