Sorry for your losses and wanted to say that i don't think there is a time limit on anyones loss. I greived for my mom who died 10 years ago now. I miss her in the physical sense but i don't miss her because i have her in my heart and anytime i want to, i can have her with me just by thinking about her. You can still have a relationship with that person, the relationship doesn't die and that is the good thing. After we have gone through the "greiving process" It does get easier but we have to greive and we shouldn't put it off. If you need to cry then let the tears flow.
As for your daughter leaving at 18 that is another loss you have to deal with but you have to let her go. I greive most of the time for my son who isn't dead but has had schizoprenia for 14 years but i greive all the time for him and the grief feels like never ending sometimes. There are all sorts of losses i think it is just a case of learning to deal with them.