Is there any expression that is the opposite of "slippery slope"?

Slippery slope is a subtle and powerful English expression. Are there any expressions that are opposite or contrasting of that expression?

The sense of slippery slope I have in mind is Small compromise, e.g. moral, leading to debasement of principles. So an opposite sense might be fortitude in the face of laxity leads to greatness.

Solution 1:

Following OP's updated clarification...

hold the line - maintain the existing position or state of affairs

...is the opposite of go down the slippery slope.

Personally, I like to suggest that at the first sign of the camel's nose poking into the tent, people should show manly fortitude. The road to Hell is paved with thin ends of the wedge, so to speak.

Solution 2:

If a slippery slope is an idea or course of action which will lead to something unacceptable, wrong, or disastrous (that's from NOAD), then one way to make an "opposite" of that would be to describe a course of action that will lead to something fruitful or prosperous – such as an education.

With that in mind, one expression you could use is toehold: a relatively insignificant position from which further progress may be made.

UPDATE: I was composing my answer as you were composing your update – now it seems like my answer is off-the-mark. Still, I'll leave it here as an example of why it's so important to clarify what you are asking about, particularly when it comes to "opposite" questions, since words and expressions can have more than one opposite (the opposite of light can be dark or heavy, for example).

Solution 3:

Slippery slope generally refers to situations where you have a positive feedback effect.

The opposite of positive feedback is negative feedback.