Don't just give your energy away, but safeguard it from those whom intentionally or unintentionally may harm you. I know the idea of family is always great, but lets be honest, some families are made up of people who are simply not safe to be around for your own mental health. So, evaluate how much of your time and energy should be spent with those who unintentionally or intentionally do you harm. I know it would be wonderful to see your family for the holidays, but if your mom is a verbally abusive narcissist who berates you nonstop, you really don't need to spend time with her, even if it's Christmas. Your time and energy is a gift, and it's not to be given lightly.
Around this time of year, we all get sucked into certain obligation engagements with others, but even in those situations you have some power. Before going in decide how long you plan to be there, where you plan to stay, what your exit strategy could look like if conversations turn hurtful, and how to care for yourself in the process. You have some power, don't let other's strip it from you.
Also, and I can't stress this enough. Sometimes people in your family may intentionally or unintentionally cross your boundaries, and although I joke with people about punching loved ones in the throat when they cross these boundaries, that is seriously not what I would recommend. However, it is important to let people know when they are offending you, and how they have crossed a boundary, and ideally how you can reconnect and have a better relationship now.
For example - let's say you are doing well on a diet, and have decided what you can indulge in over the holidays, and a loving relative makes a comment about what you are putting in your mouth. Well, first off lets be clear - This IS rude behavior. Whether they mean to be rude or not, their comment is unnecessary and impolite. What you put into your body and the choices you make about your body are your choices, and unless your pregnant or a child no one else should be informing you on your choices (unless you've asked for their opinion, and if you are pregnant only your doctor or nutritionist should be informing your choices, not well intended loved ones). So, first try a gentle approach to their comment i.e. "I apprecite your concern for my body, I am aware of the choices I am making." Then politely change the subject. If this doesn't work try something less subtle - "When you talk about what I am eating, I feel judged, which usually makes me what to eat more, I know that is not your intention, so lets just say that comment wasn't helpful, and move on." And perhaps blunt "My therapist jokes about punching people in the throat when they bring up my eating. I don't plan to punch you for that comment, but maybe the next one... (and smile real sweetly)." *Seriously don't punch them, even when they REALLY deserve it.*
OR lets say someone crosses a relationship boundary. For example, you arrive early for Christmas dinner to hear that your parents have also invited your ex-boyfriend. Again lets be clear - unless your ex-boyfriend is actually their son too (which hello, that would be a messed up boundary, and hopefully isn't the case here), he doesn't belong at a holiday meal where you will be present. You are the family member, you have priority, regardless of how much they liked your ex, or if they want to get you back together, this is a boundary violation. So, first off, I'm sorry that you're parents are totally sucking, and second you need to talk to them about it, and hopefully prevent the event from actually occurring. Now, I am likely making you uncomfortable even saying so, but even if your ex, is sitting in the living room, it is NOT too late for your parents to uninvite him. Yes, it would be uncomfortable (for your parents) and him but lets face it, it ALREADY is uncomfortable for you, and likely him. So, boundaries talk: "Mom, after relationships end it is hard. I don't feel comfortable having Jim Bob here. I know you didn't intend to hurt me, but that is what is happening, and I would like him to leave." if this doesn't work, and I know this sounds extreme, I recommend setting a more difinititve boundary. "Mom, I want to stay and celebrate with my family, but with Jim Bob here, I won't be able to do that. To keep myself safe I will need to leave. I don't want to do that and would prefer if that you choose to spend time with me, and instead ask him to leave, but if that is not your choice, I will go elsewhere, and then we will need to talk about this again after I'm less hurt and angry". Very blunt "Having Jim Bob here, is NOT okay. You are choosing him over me, and I am your family. That is not okay. Now I need to leave to be okay, but Mom, you and I are not okay because of this I'd like us to be okay again in the future, which means we will have to talk about this some other time." *consider punching mom in the throat, just kidding, please do not do that*.
So these are just a couple examples of setting boundaries after a boundary violation, but hopefully you get my drift.
Boundaries can be hard, and they are essential to keep you safe. The other thing to center on during the holiday season is your sanity, which means SELF-CARE!!! If you need permission to care for yourself when life, family and obligations are stressful here it is. Do self-care. Do what makes you feel re-energized and cared for. Honor your body and your spirit. Self care makes you able to tolerate difficult situations and make you more tolerable to others. It is not your gift just to yourself, but your gift to everyone. Self care is your friend, and during the holiday season we all need a friend.