This is reality; some parents leave their child to someone else. This is maybe due to poverty, divorce, or other conflicting circumstances. Whatever the reason is, some parents get confused and think that they have no other choice but to be separated with their child. But faith has been kind, now there is a chance for you to be together again. However, your child is now a total stranger. Many things had changed and both of you are not ready to accept that. Before you get confused again, you might want to consider thinking about these facts:
1.0 Be realistic. You child did not grow up with you so do not expect an immediate sweet response yet. Although he might be also missing you a lot, the pain inside of him is not easy to forget. His personality might not be the one you wish he has, but you must face reality. He lived without you as his parent for a long time and therefore you do not know each that well. For now, be glad that you are seeing each other again.
2.0 Tell the truth. This is the hardest part but the most important one. Your child may or may or not ask you crucial questions like why you left him. In this case, tell the truth and nothing but the truth. This may hurt both of you, but this can also be a start of your good relationship. Do not blame his other parent for what you have done. He may not understand you now but time heals wounds, even the deepest ones.
3.0 Do not force your alibis. No matter how much sacrifice you had when you left him, they will all be excuses because the truth is, you still left him and nothing can change that. Do not make him feel satisfied just because he grew up with a better life like what you always wanted. Do not justify your actions by forcing him to believe that leaving him was the best decision that time. It is like convincing your self that you did not made a mistake.
4.0 Maximize your time. You cannot bring back the lost time, but you can maximize the time left. Every minute counts so do everything to be a good parent. Make him feel proud that finally, he has now a parent to share his ideas with, and leaving him is now a nightmare from the past. Help him in all you can emotionally, spiritually and if you still can, financially even if he has now a stable career. In short, give until the last drop of your blood simply because this is what you should have done right from the start.
You better believe me with these tips. I should know because it took me 20 long years before I met my mother, and another 20 longer years before we became friends.