The rhyme never specifies that Humpty is an egg, but it makes sense that he would be- I mean, geesh, have you ever tried to put together a pieces of a broken egg? If you have ever been in a relationship where the trust was lost or "broken," then sure you have.
I believe it is a common fallacy, that trust can always be rebuilt, in many cases it can not. Love comes and goes because love is sturdy and with effort can be reignited. Trust however, much like an egg, is very fragile and when broken the parties involved need to prepared for three things;
Typically, the lover at fault believes that an apology should suffice when often that isn't nearly enough. Because of the guilt they may feel the lover at fault may be reluctant to have the discussions and answer the questions needed to help the relationship move on. Unfortunately, they opt to place their comfort before the potential of the relationship.
When couples work very hard at regaining that trust and strengthening that bond it can be a very rewarding experience. These couples should understand that though they have worked hard at rebuilding the trust is will never be the same again.
Now, that can be a good and bad thing. I personally, believe that it can be very positive if both lovers are committed to accepting that change for the sake of the relationship. The changes that may occur, can range from interest in sex to amount of daily conversations.
During the process of rebuilding trust the lover may need time to deal with their new found insecurities and that alone can be a long, yet worthwhile, journey. And the lover at fault may be encouraged to be more affectionate than usual, more attentive than usual, cut out the activities that may have caused them to break that trust... All of these things are changes and affect the dynamics of the relationship.
So often a lover will confess they "just want things to be like they use to be" that's normal- just think back to when you were dating how fresh and tantalizing things were! However, it is very unrealistic, with the ups and downs a relationship is constantly shifting and evolving- some for better and some for worse.
Don't be afraid of the growth because not only are their lessons within that growth, but it will also help you decide if that relationship is where you need to be at this point in your life.
3-Couldn't put him back together again: Often the trust will not be rebuilt and you should consider re-evaluating the relationship.
Unfortunately, most trust issues are never resolved. I can list hundreds of reasons why, but the message is not necessarily in the reasons, but that if both parties are not willing to do what is necessary and put forth that grand effort (discussed in point #1) to salvage the relationship then it may be time to let it go... be it for now by taking a break, as I discuss in my post on How to Take a Break or for good.
If you or your partner feel you are fighting an uphill battle, are growing weary, and feel trying to rebuild the trust is driving a wedge between you two instead of pulling you together before you give up consider getting a third party involved. It may be easier to address the issues with a counselor who is impartial and simply wants you two to be healthy and happy whether you are together or apart.
If that isn't an option because you don't feel the relationship is that deep then do what you feel need to do, but don't beat yourself up thinking you have failed your relationship.
It is a very difficult time for a relationship when trust is broken and often such devastation require you to have some space to Reflect, Reevaluate, and Remedy.