I have noticed this so many times when people get into a relationship.
Some become very mellow and seem happier and nicer than ever. That I can I understand, It is when they claim to be so in love and yet they become mean and nasty to others including people that once were their friends. My only guess is either they are not as happy as they say they are or Jealousy has reared its ugly head.
What are your thoughts?

Love makes everyone happy :-)
Except, as you say, the jealous.

I agree Soufie.
I have seen friendships end because a new partner was jealous of the other persons friends. Its very sad.

I have seen many of relationships end because of the same issue... I will always stay true to my friends.

ONE person must be very controlled by the other if they have to give up their friends .

Some people it seems can not handle a relationship and friends at the same time.. Have actually lost a few friends due to they found someone... I guess it is what it is... and you realize they were not the friend you thought they were..

Its kind of pathetic though ,don't you think?

Lol weird how that happens, but then when that relationship ends, who wants to be best friends again?!

It is very weird for sure. But you are right, they will have a hard time regaining their friends.

That is one negative consequence for having a big heart, more times than not, for me open arms are always given to a long lost friend, no matter the cause for the initial loss

right..I have a friend like that and right now we are in the "never hear from him anymore" stage...what do I(we) do..take them back? even though it will never be the way it was..or do we ignore them like they did us?

I think you are better off having a big heart than no heart at all.

For myself it would all depend on how much of a friend they were in the first place and what made them start ignoring me.
Maybe we could work it out...maybe not.

I would take it in stride, every situation is specific to those involved. There are some friendships that I have let go of because of that intuitive gut feeling.... Usually though, if you love that friend and you treasure what you did have previously and both sides can pick up from where it was left off like it never happened.. Certainly.

I would weigh it out when/if the time comes and go with how you feel. Mainly the question I ask myself is: "can I live MY life without that person in it?"

I see your point, but what if the reason they are not being friends with you anymore is simply because the person they are now involved with does not like you?

Agreed! The benefits far outweigh the negatives! Could not imagine the life of those without

1. Either they are blinded by one of those "so deep into a situation, that they cannot see what they really doing to loved ones around them"

2. That they really do not care.

Hoping that 1 would be the actual reason, there is really not much you can do at that point. Everyone has their own right to practice autonomy and if that is their choice in the moment to choose partner over friend, that is their choice. You can either deal with it, leave it, respect it, or dig further into WHY that partner does not like you

SERIUOSLY..WHATS NOT TO LIKE? lolJ/K
I also wonder what kind of future people that do this really have.

I have experienced this myself. But don't dispair, because after years of research, I believe I've come up with a fool proof solution to prevent this from happening to us ever again.

My research notes:
The euphoric high you experience when falling in love is comparable to the endorphin high experience when eating chocolate.

My plan: After the “honeymoon phase” is over, feed him a steady diet of chocolate.