I feel like I will never get better at chess.

Play 15|10 rapid, no blitz, no bullet.
Use all your time.
Always check your intended move is no blunder before you play it.
That little mental discipline alone is enough to reach 1500.

At your rating, learning to discover tactics is very important. Your Puzzle rating will rise alongside your Rapid rating so it's useful to do some puzzles regularly. Higher rated opponents are seeing the match further ahead than you so to get better you need to improve your ability to calculate. Puzzles put you in a situation where you have to calculate and also train familiarity with tactical patterns.

As tygxc said, you can get far by reducing blunders. I'm not a super tactical player, but I keep my pieces safe, and always in search for forks or pins. That has kept me in the 1400's rapid range (my reduced blunders have increased my rapid rating by over 200 in a month)
Another way to jump up is playing gambits, especially against lower rated opponents. Gambits can really mess your opponents and make them make errors that make the gambit worth having played.
Play 15|10 rapid, no blitz, no bullet.
Use all your time.
Always check your intended move is no blunder before you play it.
That little mental discipline alone is enough to reach 1500.
That good but if you don't have enough time then play either 5min 3 min but lot bullet

The biggest reason people struggle in lower-level chess is because of blunders. They make them in almost every game.
A mistake can instantly put you in a bad position, no matter how well you played earlier: if you had great opening knowledge, great positional skills, great endgame skills, whatever; a single mistake can change everything (you lose a piece or get checkmated).
So, how do you avoid blunders? Follow this simple algorithm:
While avoiding blunders is crucial, I also share a few basic principles with my students. These principles help them figure out what to do in each part of the game - the opening, the middlegame, and the endgame. Understanding these simple principles is like having a map for your moves. I provide my students with more advanced algorithms that incorporate these fundamental principles. When you use this knowledge along with being careful about blunders, you're not just getting better at defending. You're also learning a well-rounded approach to chess. Keep in mind, chess is not just about not making mistakes; it's about making smart and planned moves to outsmart your opponent.
@7
"if you don't have enough time then play either 5min 3 min"
++ You learn more from one 15|10 game than from five 3|2 games.

Thanks, all of you, for your feedback and tips. @tygxc I am awful at blitz/bullet, so this works best. Would 10|10 have same effect?

I have been playing chess for three years, and I know I've gotten better since then. However, what I want is to get better now, and I don't have enough time to play chess and study openings all day. I've feel as I've "maxed out" at my current, sad 900 rapid rating, but obviously I could get much better. What should I do?
You don't need to study openings all day. Just focus on one thing at a time.
Aside from puzzles, which has been suggested (and is a very good suggestion), you can take it one step further. You see an unfamiliar puzzle, get it wrong. You should ask yourself what the reasoning is to find the solution. As in, "In the future, when I get a similar position, what features can I use to guide myself towards thinking to the correct solution?"
I'll set up a very simple example.
For the sake of the example let's say we got it wrong. Well, what do we know about it? The queen and king are lined up. The knight, blocking the way, can move. If it moves somewhere random, black can just block the check; therefore, we must find a double check. Next time we see a queen lined up to the king, we should look for discovered checks, and consider double checks first.
This will help you remember the patterns of tactics more easily, and you should do the same when looking at mistakes you made in your games.

Looks like you only got 150 games. Probably play more games. My brother went from 700-1100 in two years, with no particular training, but he played 3000 games in that time, so it came naturally.
I'm 1500, and I've probably played 10k games, mostly 2min 1sec.
Hikaru Nakamuras advise to getting better below 2k rating is to do chess puzzles, and a lot of em, to improve your calculating ability. I definatley disagree with those who say learn openings. I don't know any openings past 3 moves.

It's possible that you've reached your personal limit, and may not really move up in rating.
I know that I can get a higher rating. I am capable of it, I'm just trying to figure out how.

@customgoban Yes, you are right, I'm sure. I'm just always busy, so I never have time to play, do puzzles, etc. I have beat a 1900 player, so I know I can reach a higher rating, I just wish there were a way for me to improve quickly.

I have been playing chess for three years, and I know I've gotten better since then. However, what I want is to get better now, and I don't have enough time to play chess and study openings all day. I've feel as I've "maxed out" at my current, sad 900 rapid rating, but obviously I could get much better. What should I do?
Since you probably won´t play chess for a living the relevant question is: Do you have fun? If it´s fun - keep playing. If not - what´s the point?
I have been playing chess for three years, and I know I've gotten better since then. However, what I want is to get better now, and I don't have enough time to play chess and study openings all day. I've feel as I've "maxed out" at my current, sad 900 rapid rating, but obviously I could get much better. What should I do?