How to dampen a value but also do the reverse?

Credits to Goulstem How would I make this script slow down before it his the max/min value and then speed up when it goes away?

local wag = 1; --number
local bool = false; --bool switch
local MIN,MAX = -33,33 --bounds
while true and wait() do
    if wag < MIN or wag > MAX then
        bool = not bool --switch the bool
    end
    wag = (bool and wag + 1) or wag - 1
print(wag)
end