chronic
never ending/non stop
incessant
never ending/non stop
inexorable
never ending/non stop
interminable
never ending/non stop
relentless
never ending/non stop
perennial
never ending/non stop
fitfully
irregular/periodically
intermittent
irregular/periodically
spasmodic
irregular/periodically
occasional
irregular/periodically
sporadic
irregular/periodically
terminate
end/ stop
culminate
end/ stop
cease
end/ stop
onset
opposite of end/ stop
ephemeral
short lived
evanescent
short lived
fleeting
short lived
transient
short lived
transitory
short lived
allay
calm down/ make better- diminish or put at rest the fear, suspicion or worry
alleviate
calm down/ make better
ameliorate
calm down/ make better
assuage
calm down/ make better