Reset variable to default value

i mean reset value to default while executing .for example you have a variable called “power” with defaul value 50. then you use …hmmmm…potion which makes it increase to 100 for 5 seconds and after 5 secs you need to reset it to 50. i think it would be useful to have some node which resets var value instead of having 2 variables “currentPower” and “defaultPower”