Beginning of an End or End of a Beginning??

In life I have often come across a situation where everything around me has gone crushing down on ground and many a times i have seen a new thing being created out of that debris.....I often wonder what should be my reaction to such situation..shall I be happy that the debris have given rise to something new, more beautiful or shall I be sad that whatever was created with so much of efforts, hard work, creativity has gone crushing down on ground and thereby has lost its very own existence....
I seriously have not understood how to tackle this tricky situation....relationships often woven with so much of efforts reach to a point from where they can not move on so at this point shall I sit and weep because they can not move on the way I always thought about them or shall I be happy that I have got the maximum output from that relationship which I could have ever got.... shall I hold it tight with my both hands and try and hang on that burdensome relationship or shall I let it go...... let it go to get it replaced by a new positive, fresh relationship which may bring in some fresh air in my life?
Am I scared to loose the present or am I too skeptical about the future? Travelling into the unknown passage often seems exciting when done by other but when comes to me why am I so scared to take that passage....why am I scared to end whatever I have started and begin something new....what it should be a beginning of an end or end of a beginning????