Ambitious people like us can't help but compare ourselves to our peers.
Often as these individuals experience success, we feel less successful by comparison. And so a common human reaction (whether we realize we're doing it or not) is to slowly distance ourselves from these friends and colleagues.
Sure, consciously you may tell yourself you just "fell out of touch"...but subconsciously you may be deliberately escaping the discomfort of the harsh self-evaluation that comes with being around them.
Ironically, the need to "keep up" with our peer group is one of the strongest motivational forces in the entire universe and provides one of the greatest fuels for our own success.
The need to "belong" and the resulting pain when we feel we don't can be a true gift...if you choose to embrace it instead of running from it.