Yes, you can terminate a revocable trust at any time so long you are competent to do so. If you have transferred any property into the trust, you'll want to make sure to transfer it out of the trust (as merely revoking the trust will not accomplish this automatically). While you can simply write "revoked" on each page, what I would suggest is that you use a revocation like the one below, and sign it in front of a notary, and attach it to the trust itself and keep them together.
REVOCATION OF THE ***** ***** REVOCABLE LIVING TRUST
I, ***** *****, hereby revoke the ***** ***** Revocable Living Trust, created by Declaration of Trust signed August 18, 20xx, according to the power reserved to me by Part _____ of the Declaration of Trust.
All property held in the trust shall be returned to the grantor.
_____________________________________ Dated: ______________
***** *****, Grantor and Trustee
Certificate of Acknowledgment of Notary Public
State of _____________________
County of ____________________
On __________________, before me, _________________________, a notary public for said state, personally appeared _________________________, proved to me on the basis of satisfactory evidence to be the persons whose names are ***** ***** the within instrument, and acknowledged to me that they executed the same in their authorized capacities and that by their signatures on the instrument the persons, or the entity upon behalf of which the persons acted, executed the instrument.
Witness my hand and official seal.
NOTARY PUBLIC _____________________
My commission expires __________________.