Asking for more of something isn't a sign of being ungrateful; it's a sign that you liked it, that it felt good, brought you joy, enhanced your life and/or someone else's, and you want more of it so you can continue experiencing those great effects. You can be grateful for what you have and still ask for more. There is nothing wrong with asking for more—a whole lot more—of what you already have, just had, or maybe haven't even experienced yet (in which case you would ask for the initial experience).
When you enjoy (or need) something, asking for more is a natural response. When you're a guest at someone's home and they feed you really awesome food, and you want more, you politely ask for it. It's a compliment of sorts. It says, "Hey, you really did the damn thang with that food, and I enjoyed it so much that I'd like to do it all over again." People generally like it when you express that something they have given you was not only appreciated but also that more of it is desired, if possible. The universe is like a big "all you want" buffet, where there's no limit to what you can have. You're a guest here, and if you need or want something, all you have to do is ask.
Settler's Gratitude is when you're playing small, not confidently and passionately asking for [more of] the things you need and enjoy (things you know deep down that you deserve). It's equivalent to quietly accepting an unfulfilling relationship, being meekly grateful for the [inconsistent] times your mate actually treats you the way you want, and hoping that one day, if you're grateful enough for "the little things," the person will kick that good treatment into overdrive. Because you're afraid of being an ingrate, afraid that asking for more is tantamount to balking at your [lovely but inadequate] blessing, you lack the courage to assert yourself in said relationship and make it clear that being treated well "sometimes" isn't acceptable, that you enjoy and deserve being treated right all the time. If, when frustrated enough, you do try to assert yourself and pursue your ideal relationship, you do it while feeling apologetic and guilty. Part of you is like, "This isn't working for me; I deserve, need, and want more"; the other part of you is like, "Dang! How ungrateful are you right now? Think about that good thing your boo just did for you last month! It was so special, and now look atcha! You can't be content with and focus on that goodness, that blessing; you just gotta be negative by thinking about how this isn't enough and how you want it to be like that all the time. See, that's what's wrong with you; that's why you can't get ahead in this relationship. You just refuse to be happy with what you have. Ole ingrate."
No matter what disheartening drivel your ego tries to get you to believe, the fact is this: you deserve the buffet of wonderful treatment and perks in your relationship, and in all of your life's scenarios.
Now, don't get it twisted: gratitude is always crucial, and it's a major key to getting ahead in life quickly. Gratitude is encouraged to be in the front seat during your journey, and you're urged to employ it daily. As a matter of fact, the truly courteous thing to do before you ask for more of something is to say thank you for what you were given or experienced. If you wanna uplevel your request game, you can say, "Thank you [Universe/God]! I enjoyed that! I'd love an unlimited supply, please!" And you know how sometimes when you're asking someone for something, and at the end of your request you say, "Thank you, in advance"? You can do that with your source, too. "Universe/God, I need/would like XYZ. Thank you in advance." I know these options may seem extra'd out or silly, but remember that the idea is to help you learn how to confidently do two things simultaneously: be grateful while requesting more because you comfortably acknowledge that more is not wrong, especially when it's necessary to function at full capacity in life. Some people have no problems aggressively asserting themselves in pursuit of more when something's not enough. Good for them. Maybe that's not you, though—but you need to get better at your asking so you can advance in life, so, hey, maybe you have to start off being a lot more diplomatic than the veteran guilt-free asker. The point is to finally feel good about your request, to not feel like you have no right to be asking. If you have to pretty-up the language a bit in the beginning, then so be it.
You can totally go about getting more while being grateful and courteous.
Another important aspect of this concept is that it's important to keep asking for more (in life) when your whole need or desire isn't met. Nobody but you can properly assess when your needs and desires have been fully met in your various scenarios. It they're not, then yes, give thanks for all the parts that are, the steps that are leading to the full fruition of your needs and desires, but definitely continue to pursue the rest. It's your job to make sure your best interests are tended to, so don't apologize for doing so, and don't let people make you think you shouldn't be asking for more or better for yourself. What you want or need for you is none of their business.
Now here's the hard part: Not asking for what you need and want is a sign of low self-esteem. Huh? How, Sway? Because encompassed in self-esteem (which equates to self-respect) is self-care, your depth of it, and how you feel about engaging in it. Self-care involves doing and pursuing all the things that are in your best interest—confidently, not timidly or halfheartedly. Any time you're struggling to do what's best for you, it means your self-care meter is out of whack. You are really the only person who can spearhead taking care of yourself properly (unless you're having a medical emergency in which you're unconscious and need medical professionals to decide your best interest for you). You're in charge of making sure to initiate and follow through with your pursuit of happiness. If some part of doing that makes you uncomfortable, it's time to dig deep and ask yourself why. Because you have every right to be happy in this life. Going after it, asking for it, and feeling good about making moves toward it, isn't intended to morph into an emotional crisis (which subsequently blocks your advancement). If you're not passionately and unapologetically compelled to pursue the peace of mind and overall life you want, then what's an even more painful pill to swallow is the fact that you'll be hard pressed to acquire the [full] outside support you need to get there, because what you get from your environment is a direct match to what's going on inside of you.
Getting yours begins with your having a high level of determination to do so. Look around you. What do you have that you enjoy, love, appreciate, and desire more of? What in your life makes you feel your best, feel at peace, feel confident, and helps you feel like you're adding value to the world? Whatever those things are, I encourage and invite you to practice expressing your appreciation for them, and then having the chutzpah to ask for more—as much as you think you'd like, that will allow you to keep that smile on your face and that contentment in your heart. You deserve it. Every day.