I just wanted to share this. I have two DSSs, 16 and 18, have been their StepMum for 12 or so years. It has been at times extremely difficult, I have given everything I can into being and doing the best for them, and yet have frequently and lastingly felt like they hated and resented me (particularly DSS2, but that's another story).
Recently DSS1 has been staying with us to study, - I dreaded it, I thought it was going to feel like an invasion, as it has often been (invisible woman emoticon, you know what I mean), BUT it's actually been ok 
He comes in from school, cheerful, sociable - greets my two DSs, tells me about his day - how his exam went, "may I just have some juice and toast before I get on with studying?" And up he goes, shuts his door and studies and studies . Then he'll be down to tell me how he's getting on, and if he can get this pass mark then he'll be ok for that etc - and then off he goes again.
I'm actually feeling proud.
there's more..
He's grateful for the mound of food I give him being fed a decent meal.
He asks if it's ok before taking a shower (we're all sharing one bathroom at the moment)
He makes his own packed lunch and asks if there's any more milk before necking the last lot
Because he knew he was coming later in the evening one time he told me not to include him in the meal, and brought his own takeaway with him
So, this is what it feels like to be appreciated.....
He's growing up into a really pretty decent human being.