Of course, here's a suggestion for how you might express those feelings:
"My dearest [Mom's Name],
It’s been a long and sad journey without you, my sweetheart. I often find myself reflecting on the moments we shared, and I miss you more than words can express. Your love and guidance are always in my heart, and I wish I could share my life with you once more. Know that you are always with me in spirit.
With all my love,
[Your Name]"
Feel free to adjust any part of it to match your personal style or specific emotions.