I don't know if I am cursed or something. If I sell a coin now from airdrop/bounty few days later that coins increases much that you will regret selling. If I hold a coin from airdrop/bounty again that coins price decreases much that you will regret not selling right away. I'm confused now whenever I sell the price increases and when I hold the price decreases. Am I cursed?

You and I both Op, we are both cursed. Suffered the same fate as well. But seriously, once I sold the token, I do not care if it pumps after. I only sell when I am satisfied with the profit. If I failed to take profit on a pump, I just let it go and take it as a lesson. It is no use to beat yourself just because you failed to sell on the best price.
Highs and lows are normal trend of the market and it's something that we have to be aware of. It's important that if we engage in the field of crypto we have to embrace its nature, gain knowledge, know and understand its functionalities. Things may not turn out the way we wanted it to be but don't lose hope, stick to your goals and change the strategies. Life's like that, if things don't turn out well, never fear failure, make it as a motivation and learn from mistakes.