今年の運は大吉と出ました。これを機会に結婚しようと書きたい。

Subject:  A great fortune for me this year.

Dear XXX,

I have found out that my fortune this year is the best in 12 years.  The relationship between you and me has been wonderful and we are congenial with each other.  Shall we start our new life together?

Love,
[your name]