I'm sorry that your mom died and that you didn't get to resolve these issues with her before she did.
These things do matter. The fact that my mom died and that I didn't get to share any of my adult life with her is probably the single most important influence on who I am as a person.
My mom died during my first year of college so there's a lot of things I wish she could know about me. She never saw me graduate from college (in three years, which was her dream for me--she would have been so proud), she never saw my career take off, she never saw the book I wrote. My sister is younger than me, so my mom never even saw her go to prom, graduate from high school, graduate from college, get married, have kids...the list of things my mom never got to see that both my sister and I wish we could have shared with her just goes on and on.
But, at the same time, if my mom had lived, my life would have been completely different. It's ironic, but I probably wouldn't have graduated college in three years, I wouldn't have moved to California, I wouldn't have the career that I have (or even have written a book). Although not a day goes by that I don't feel the hole she left in my life, I also know that her death made me stronger and that she continues to shape who I am as a person even today. I also know that when she died, she did so knowing that she had raised us as best she could and that she knew we would succeed without her, even if she didn't get to see that success.
I think that both my sister and I desperately wish our mom could see how we turned out but I don't really have an tips on how to deal with it. I've always felt like I didn't have a choice. She died and my life goes on. I can't change the fact that she died so there's nothing I can do but continue to live my life the best way I know how without her. In situations where I feel unbearable emotional pain, I always just tell myself that keep breathing and eventually time will pass and I'll get to a point where it is bearable. I like that, 20 years after my mom's death, I continue to grieve for her because it does make her a force in my life. I want to always feel the pain that I feel about her death and I don't want to ever feel like my life is complete without her. I try to look at these disappointments as a blessing because they remind me of how important she was to me and they make her a continual presence in my life. I'm not sure if any of this makes sense.