You should always remember that people’s ideas, emotions and opinions keep on changing. Everything changes. Many friends become enemies & enemies become friends. You're friends with somebody & suddenly for no obvious reason they become ur enemy. You haven't done anything wrong to anyone, yet they turn out to be unfriendly towards you. Sometimes people who you don't even know will come to ur help. You haven't done them any great favour, yet they help you. This friendship & animosity works on a deeper principle called karma.

If ur time is good, ur worst enemies also start behaving like ur friends. And if ur time is not good, then ur closest friends too will misunderstand you & start behaving like ur enemies. If you look back, you will realise that somewhere you have sown the seeds for a tree of thorns. So today, or sometime later, you will surely have to reap the thorns of that tree.

There are two types of karma: one that immediately gives fruit and second, one that yields fruit sometime later. For example, if you place ur hand in a fire, you will immediately get burnt, right now, not tomorrow or any time later. But if you sow a mango seed today, it will take a few years for it to grow into a tree. In the same way, some karmas yield their fruits almost instantly, while some take time to bear fruit. 

Look back at ur own life & see how many challenges you have had and how you have sailed through them & come out. This will give you confidence. The other option is to realise that you have to pay some debt, and so you are undergoing what you are undergoing. But do not think that every problem or suffering that you go through is only because of ur actions from past lifetimes. Some of it also comes because of the foolishness and ignorance from the present lifetime also. 

To free yourself from the results of past actions, you should regularly practice sadhana (spiritual practices).When you see this from a bigger perspective, great inner strength dawns within you and you are able to smile through any situation.

Gurudev Sri Sri Ravi Shankarji