This is a tricky situation. To start with no one can ever understand the other person fully. In fact we ourselves cannot understand our own complex motives hidden carefully in a many-layered personality. So sharing half truths, – and all we know is at best half truth, is not at all a wise thing. As such human mind has a habit of taking only those things that suits its purpose of the moment. Often we fill in the blank spaces of any event based on our limited understanding of life, so sharing everything even with our best friend or family members is to create needless confusion.
But the other part is tricky and brings in the element of hiding our feelings for one person with someone we love and plan to build our life together. I presume this based on the tone of your letter. Imagine if and when your boyfriend discovers it. That may be devastating. If you wish to build a lasting togetherness with your boyfriend then there are one of the three options.
1. Share with him your feelings for the other person. As we discussed this is likely to create more confusion than clarify things. But a long term relationship requires mutual trust and hiding is never a good thing in this situation.
2. So the other option is to reorient your relationship with the person purging it out of anything that will be detrimental to the trust you need to build with your boyfriend. Give it a healthy direction which means not only absence of physical involvement but also emotional dependency. It is difficult to invest emotions in two persons with same intensity. A healthy friendship means keeping it largely to a sharing of intellectual ideas, caring for each other, a mutual affection and, standing by in times of crisis.
3. If there is physical involvement or deep emotional dependency then it is best to break off one in favour of the other. The mind is capable of stepping into number of boats at the same time and the animal vital also capable of roving and roaming in different fields of pasture. But the heart is one and cannot easily love more than one person at the same time unless deep within it is surrendered to the Divine and needs nothing from anyone. In that case the whole quality of its love changes and can no more be bracketed into boyfriend or girlfriend.
Affectionately,
Alok Da