Friends ; a true definition

Not too long ago ,  I had a friend ( still are friends but no longer a close pal ! ) , as usual , asked for help concerning the flower arrangements for her wedding . Yours truly as always , as a good friend was more than happy to say ' yes '  I can help you . Then on the eve of the wedding , she sms'es me and tells me she does not need my help as her sister in-law has made all the arrangements ................. If you do not need my help , don't you have the bloody courtesy to inform me earlier rather than waiting at the last minute ??? !!!
In situation like this, I start to rethink the true meaning of the word ' friend '. How come it cannot be as simple as those of Joey, Rachel, Monica, Ross, Phoebe and Chandler ? I know the relationships between each of them are a bit ' messed-up ' but look how they still stick together through thick and thins. OK, OK... I do realise that ' Friends ' is just a sitcom, but still... People say in a relationship you have to 'learn to give and take', while other people say that 'giving is better than taking'... I believe 'relationship' also refers to 'friendship', right? But how much should you give and how much should you take? Is there a predefined quota or limit? Are we supposed to weigh the amount of giving and/or taking done from each party? Should we be even weighing them in the first place? Ok, fine. Maybe we should not weigh. But, doesn't the phrase ' Enough is enough ' counts? I guess another characteristic of being a friend is 'to forgive and forget'. Recently, I watched Miss India pageant where they asked each final contestant to answer this question " Forgive and Forget is easier said than done - What do you feel ? " I remembered one of the contestant replied that ' To forgive is to forget, so if you do not forget then in means you're still holding a grudge and you haven't forgiven the person ' . True enough. However, it is hard to forget whatever a person has done to us. Everything leaves a scar. Physically, emotionally. So, what is the true meaning of the word ' friend ' ? What are the characteristics of being a friend ? So many questions , so little time...