I couldn't care less what the price is doing at the moment. Doesn't rock my boat at all..
So from my perspective it is as stable as a rock.

The market price is a public weighted average of the value people give to it privately. Many people value it much higher and won't sell. Others value it lower and won't buy.

The value I give to a bitcoin hasn't budged an inch in the past months. That is the only measure of stability I care about when looking at bitcoin.