You could have realised that your friends no longer communicate with you as they did before or your phone does not ring as often as it did.
They also do not invite you to their events as they did. It could be that your behaviour has pushed them away.
There could be several things that you do that do not sit very well with them such as:
1. Gossiping behind their backs
Your friends could have realised that you gossip about them behind their back and laugh at them for mistakes they once did. This will keep them away from you. Always consider how you will feel if it was you they were gossiping about.
2. You judge them
You could have driven your friends away by judging almost everything they do instead of supporting and showing them how much you care. Remember that no one is perfect and your close friends expect your affection and honesty.
3. You never initiate a conversation
You probably do not take any initiative to check on your friends either over the phone or physically. If they realise you do not make any effort to keep in touch, it will reach a time they will never check on you.
4. Speaking negatives all times
Your friends will not entertain listening to your negative thoughts about life especially if they have positivity with them. No one will stand a conversation that is filled with complains and negativity because this might affect their outlook on life.