Regaining the lost stickiness of your ping pong paddle can be accomplished in a few ways. Here are some tips:

1. Clean Regularly: Dirt and oil from hands can accumulate on the paddle surface over time, reducing its tackiness. Use a specially formulated table tennis paddle cleaner or a solution of mild soap and water to gently clean the rubber surface. Be sure to dry it thoroughly afterwards.
2. Boosters: You can use commercial boosters available in the market that are designed specifically to increase the tackiness of your paddle.
3. Rubber Revitalizers: There are products available that can rejuvenate the rubber and restore its original stickiness. These are usually applied onto the rubber surface and left to dry.
4. Replacement: If the rubber is too old or worn out, you might have to consider replacing it. Sometimes, no amount of cleaning or boosting can bring back the original stickiness if the rubber has deteriorated significantly.

Always follow the manufacturer's instructions when using cleaning solutions, boosters, or revitalizers to prevent damage to your paddle. And don't forget to store your paddle in a case when not in use to protect it from dust and damage, which can help maintain its stickiness for longer.