Many of us have a hard time saying, "No". We're socialized to help, to nurture, to put others first; to never turn down opportunities or disappoint. And so we take on work that we don't need to take on.
But saying no is an act of self-care and it should be acted upon.
We attend events that we don't want to attend. We go on dates when we'd much rather be doing laundry or catching up on emails or reading. We have a drink when we'd prefer to stay sober. We buy things we don't want to buy or donate to causes we don't want to donate to.
The problem statement: We don't want to "let people down."
But this isn't a way of living. Not only do we experience all the negative consequences mentioned, but we rarely get to experience the life we want to–as our needs are always put to the side to make room for someone else's.
Some unhelpful beliefs lead to always saying yes
Never turn down an opportunity
Truth: There are endless opportunities, and if you take them all on you'll live in a constant state of stress. Consider saying "No" to one opportunity being a way of saying yes to yourself.
Always put others first/Being "selfish" is a bad thing
Truth: We need to be selfish! No one else is living our lives for us. The relationships in which you're giving all of yourself will improve drastically if you set boundaries and engage when you want to.
Always follow through on what you've committed to
Truth: Learning how to say "No" will actually drastically decrease how often you "flake," because you won't commit to things you ultimately bail on; however, there will always be times when you need to cancel plans in order to take care of yourself which is OK.
If you can, you should
Truth: Just because you can help doesn't mean you should. If you're feeling burnt out and pressured into helping, chances are you need to take that time to look after yourself.
This is one reason for your ever-increasing stress.
The ending words
Saying "no" can be seen as a sign of weakness both in your heart and in the people you work for. But, understand that saying no is not a weakness but people-pleasing definitely is. You don't have to do it when you don't feel like it!
Stick to what seems good to you, what makes you happy, and leave the guilt of not standing up to someone else's expectations. Live your life your own way.