Leonard Hofstadter is one of the main characters in the iconic sitcom The Big Bang TheoryAs an experimental physicist at Caltech, Leonard is extremely bright and gets to work with his best friends Sheldon, Raj, and Howard. However, as smart as Leonard is, he sure has made some mistakes in his life that viewers can learn from.

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With a dry and callous mother, an overbearing roommate, and a girlfriend who's the complete opposite of him, let's take a look at 10 mistakes Leonard made throughout the show's 12 seasons and how we can learn from them.

DON'T CHEAT ON YOUR SIGNIFICANT OTHER

Big Bang Theory - Penny and Leonard talking in bed after getting married

It was shocking when Leonard told Penny he cheated on her when he was away working on the North Sea. To make matters worse, he told Penny this information when they were on their way to their own wedding.

While penny played it cool for a few hours, resentment and trust issues surely followed. But his indiscretions with Penny wasn't the only time he messed up in a relationship. He also cheated on Priya with the woman he met in the comic book store.

LYING TO YOUR BEST FRIEND NEVER WORKS OUT

Leonard and his itchy sweater on TBBT

Leonard lied to Sheldon quite often. Thanks to Sheldon not understanding sarcasm or realizing when Leonard was telling a white lie, he got away with most of the lies he told. But on the rare occasion when Sheldon did find out about Leonard's lies, they created more drama than was originally needed.

In the seventh season, Leonard caught himself in a lie that was years in the making when he told Sheldon he returned a DVD when he actually didn't. This led to an epic battle of revenge. Something similar happened in season three when Leonard messed with Sheldon's project in the North Pole.

AND NEITHER DOES LYING TO YOUR PARTNER

penny fools leonard - the big bang theory

For as devoted as Leonard is to Penny he sure does lie a lot to make sure the night ends in love-making (or "coitus" as Sheldon would say). In the seventh season, for example, Penny began reading Leonard's mother's book for her psychology class.

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This embarrassed Leonard greatly and the only thing that seemed to make him feel better was Penny taking her clothes off. Seeing the connection, he kept this 'woe is me' gig going for a long time before Penny finally caught on. The result was Penny shunning him and getting his mother involved, which was major payback.

DATING YOUR BEST FRIEND'S SISTER CAN END IN DRAMA

Priya helps Leonard walk without his glasses on TBBT

Getting involved with your best friend's sister sounds like a disaster waiting to happen but Leonard followed his heart when it came to Priya. To be fair, while it drove a wedge between him and Raj, Priya really was a good match for him. They had oodles in common, she was driven, and she pushed him to do better. But his relationship with her came at a cost.

His relationship with Raj suffered and drama hit the fan when he cheated on Priya. The two broke up and thankfully, Raj and Leonard were able to pick back up where they left off.

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Big Bang Time Machine

When it comes to memorabilia, Sheldon, Leonard, Raj, and Howard take it to another level. They buy toys they can never play with and collect comics that one day could be worth a fortune. But in "The Nerdvana Annihilation," Leonard went too far when be bought a  full-size replica time machine from the movie The Time Machine.

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He bid $800 for it (without looking at the size of the time machine) and ended up winning. When the time machine was delivered, the gang was stuck with a massive time machine in the middle of their living room before deciding to move it from house to house.

THINK BEFORE YOU SPEAK

leonards radio interview - big bang theory

For a genius, Leonard can do some dumb things from time to time. In "The Retraction Reaction," Leonard did a radio interview for "Science Friday" where he publicly embarrassed the physics world and Caltech. He basically said that they're giving millions of dollars to prove theories and all of their work is for nothing because they haven't proven anything yet.

His horrible interview almost got him fired and had donors wondering why they were giving Caltech all this money if physics was a dead end. It also deeply upset Sheldon who saw physics as his "lady" and was offended by his words.

LIVE YOUR LIFE WITHOUT FEAR OF FAILURE

leonards brothers letter - big bang

In the 11th season, Leonard gets a holiday card from his brother stating all of the cool things he accomplished that year. Realizing how much of a go-getter his brother is made him question his own goals. What had he accomplished that year anyway? With Penny's help, the couple realized they didn't do anything worthwhile and often don't do things for fear of change.

Leonard didn't do anything noteworthy at Caltech, Penny didn't like her job, and they never followed through with vacations or activities. Seeing their lack of achievements and lust for life should be a lesson learned for viewers; to get out and live life to the fullest.

DON'T HIDE MONEY FROM YOUR WIFE

Leonard and Penny argue at the cabin in The Big Bang Theory

For a long time, Penny was not very good with money. She had mounds of credit card debt, bought frivolous things, and didn't save. Leonard, on the other hand, seemed more stable with money and knew how to spend it wisely. But in the seventh season, a drinking game at the cabin revealed that Leonard had a private bank he was hiding from Penny.

With a couple of thousand dollars in savings, he didn't want Penny to blow through it all on senseless stuff. And as one could imagine, Penny felt betrayed. Being transparent with finances seems like a no brainer in relationships.

BE SENSITIVE OF OTHER PEOPLE'S FEELINGS

Leonard and Penny look angrily at each other in The Big Bang Theory

Leonard may say some silly things from time to time but he's a good person at the root of it. He just doesn't know when to stop talking or how to say things delicately.

When Penny was having a rough patch in her acting career, she asked Leonard if he thought she had what it took to be a star. He answered honestly but unfortunately, his honest answer wasn't kind. He did something similar when he and Penny first started dating and he told her he didn't care that she wasn't "smart" or that she was uneducated...

DON'T STICK YOUR NOSE WHERE IT DOESN'T BELONG

SHELDON AND LEONARD ON THE COMPUTER - TBBT

Leonard is apart of a very tight-knit group where everyone has similar interests and plenty of things to talk about. But there are times where Leonard sticks his nose in situations that didn't concern him, causing tension in the group or in his relationship.

He wrote Penny's first college paper (even though she never asked him for help), he helped Sheldon clean her apartment when she was sleeping (which was all kinds of creepy), he "helped" disapprove Sheldon's theory without alerting him, and the list goes on. Maybe it's best to stay in our lane and only handle issues that concern us?

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