He is controlling and inflexible...

I am a 31-year old woman and have been re-evaluating my relationship with my partner since the Covid-19 pandemic. We were in lockdown and being able to see this relationship in close proximity taught me that it is not as healthy as I assumed it was. He is controlling, not flexible with anything, and doesn’t place my interests above his own. This selfishness was probably always there, but I couldn’t see it because I was so busy with other things in my life. I believe this is not going to work in the long run, and I want to end it. Should I give him a chance to change, or am I being irrational given that the pandemic must have affected many relationships the same way?
You’re right about the pandemic having an adverse effect on many relationships, but there is also something to be said about adversity and what it teaches us, not just about ourselves but about those close to us. If you saw something in your partner that you hadn’t noticed before, you should treat it as a learning experience and trust your instincts. If someone doesn’t rise to the occasion in times of trouble, and you believe this isn’t good for you, the sooner you put your needs first and move on, the easier it will be to get to a place of good health. I suggest you don’t look at it as an aftereffect of the pandemic, and simply consider it as a relationship where one person isn’t right for the other. You can always speak to him about this and see how he reacts, or if he is willing to make changes, but that depends only on whether you see a future together.

The more I try to be nice to my friend, the harder she is to please. How can I fix this or learn to cope?
The onus of fixing or coping with this isn’t on you alone. Friendship, like any other relationship, is about mutual respect. Reconsider this one.