There’s a finality to endings that’s bittersweet. 

The completion of the thing - especially something that’s absorbed us wholeheartedly and then come to some natural conclusion - almost always results in a mixture of emotions. 

There’s the joy that comes from the experience (the good times, the contributions, the confirmations) which can be considerable and, at times, overwhelming. This joy is experienced both during but also in retrospect, once we’ve gained an appreciation of those aspects we may have taken for granted.