My changes would be along these lines...
I am thankful for my heart - it gets stronger with every run I complete and every time I open it to possibility.
I am thankful for my children - they have taught me true joy, compassion, and love like no other.
I am thankful for each day that I am here - while I am sometimes scared of what is still to come, I am thankful that I get to be here and make an impact.
I am thankful for a man who loves me - my husband who builds me up every single day and embraces who I truly am.
I am thankful for the struggles I have faced - they have taught me how strong I truly am, and given me unparalleled perspective.
What are you thankful for? What will your mantras of gratitude be?