(adj): vs. sporadic) -- (occurring without interruption; chiefly restricted to what recurs regularly or frequently in a prolonged and closely spaced series
(adj): continually recurring to the mind
(adj): vs. forgettable) -- (impossible to forget
(adj): vs. caducous), lasting -- (retained; not shed
(adj): stubbornly unyielding
(adj): vs. docile), obstinate, unregenerate -- (tenaciously unwilling or marked by tenacious unwillingness to yield
Learning is persistant because you can't give up.