With me you can make a difference.
With me reversed, I'll rise and I'll fall.
2 Answers
You are the word:
EDIT - when you 'edit' something (for instance, a post on a StackExchange site, like this one) you quite literally make a difference by altering some of its content.
Reversed, this then gives you:
TIDE - the level of the sea rises and falls every day, as a result of the tide, influenced by the pull of the moon, giving us high and low tides.
A bit of a stretch, but i think you are
Minus
With me you can make a difference.
Is you want to know the difference between two numbers, you will subtract them with a MINUS sign
With me reversed, I'll rise and I'll fall.
The SUN does raise and fall daily and in reverse you clearly tell us "SUN I (a)M"