Too much contact after no-contact and/or in the initial stages gives a false sense of interest and momentum. Even if it’s your ex initiating most of the contact, at some point, they will pull back to reset the pace to what they are comfortable with and/or where they are emotionally. This can happen whether they are somewhat interested or very much interested.
When this happens, you will become anxious because you think you did something wrong to make them pull away and/or act needy because it looks like they are no longer interested when all they are doing is resetting the pace to what they are comfortable with..
To prevent this from happening, build up contact and connection gradually.