Simply replace the unfilled areas such as "" and "[date]" with your information.
Dear [name of love interest],
I have very much enjoyed the time we have been spending together recently. But I feel like you are pushing for our relationship to extend into the next level. I am interested in continuing our relationship, and growing it, but I am a very cautious person.
Please understand that I need more time, not because I am not interested, but because I am naturally slower at this type of thing. Commitment means a great deal to me and I don't jump in lightly. When I do jump into a deep relationship, you can be sure that I am whole-heatedly committed.
Please be patient with me as I adapt to this new relationship.
With great affection,