It's another Allan Taylor song, so you'll be able to pick it up from the source quoted in the other string. Off the top of my head, the lyrics as sung by The Fureys are:-

Sometimes I know I'm forgetful,
Things roll by from day to day.
Sometimes I don't bring you flowers
When I've been away.

Chorus: Sometimes I'll forget to tell you -
I'm can't promise that I won't.
If I forget to say I love you,
It don't mean I don't.

Sometimes I know I get careless,
Lose my temper and I get mad.
And I forget to say I'm sorry.
I know it makes you sad.

So know you know - at last I've told you.
Think on this when things go wrong.
And if I take my time to hold you,
Don't think you don't belong.

Chorus: Sometimes I'll forget to tell you -
I'm can't promise that I won't.
If I forget to say I love you,
It don't mean I don't.