Saying good-bye is never easy. Even when we leave behind situations that are painful, it still requires an adjustment, for pain, too, is something which can be missed once gone.
Every relationship, every situation, is for a reason. It may be that some knowledge of current, must be brought forth into future endeavors. Usually, if paid heed and utilized correctly, this new knowledge can be beneficial to all involved.
Grow. Never stop adding to the learning adventure. Stretch your comfort zone, move beyond what you may see as your capacity. There is always room for something greater. You have so much to offer, and while others offer their own experiences for lessons, you can do the same for them.
Your life is valuable, your knowledge is perfect and when used for good can shift the world view and path toward the outcome of peace and compassion. The seeming negatives, which undoubtedly have been yours, are teaching tools. For others, and also for self. Moving beyond the pain they may have caused, increases care for self, and for all in the world.