こんにちは！ I'm just a beginner in Japanese (started my Japanese self-study from this March) but now I'm working in a Japanese company in Tokyo. Since most people in my company can't really speak English, I have no choice but to use Japanese for my daily conversation. Until now I can somehow manage basic conversations with my co-workers, but I know my Japanese is very beginner-level. I follow the rule to use formal Japanese (ます/です) instead of (ある/する) mostly all the time to avoid being impolite. I know it makes my Japanese sound unnatural/strange but I think it's a safe choice, at least in the workplace environment. But the more I'm familiar with the language, the more I feel the need to use less such honorifics. I try to listen to others' conversations to see if ある/する is used by juniors to seniors or not, and they do use it, much more than ます form, even with the boss. I find it so tiring to go with such sentences like: 「昨日は大阪に行きましたけど、雨でしたから出かけなかったです。」 Just for example, how would you guys make the above sentence sound "more natural"? Can I say like 「昨日大阪に行ったけど、雨だったから出かけなかったです！」when I talk to my boss? I really need more time to be able to "sense" the language and its politeness, before that よろしくお願いします！
Usually you should use です/ます only at the end of the sentence.
In the middle of the sentence you can use informal tense (ある/する). So you can say:
It is very difficult for foreigners to know when to drop politeness and be informal, especially if you are talking to your boss or someone superior.
It is never a bad thing to be over-polite, while making a mistake and being rude can get into trouble.
Using です・ます体 (desu/masu forms) isn't very unusual, at least not in my opinion.
In fact です・ます体 is more so like the absolute middle ground/standard level of politeness when it comes to that sort of thing. If you really wanted to be like "polite" polite with your Japanese, speaking to your seniors and stuff you'd use 尊敬語 and 謙譲語 (sonkeigo and kenjougo) which is like the definitive formal and polite manner/form of speech in Japanese, where almost everything becomes different, e.g. いる, 行く, and 来る become いらっしゃる, 食べる and 飲む become 召し上がる (meshiagaru, you'll hear this at restaurants at lot from the staff: 店内で召し上がりますか? (will you be eating in the restaurant?)), する becomes 為さる (nasaru), and so on and so on. All of the examples I gave are of sonkeigo which is what you use to your superiors as it basically embellishes their actions as being above you in a way, sort of.
So in short, です and ます are honestly completely normal to use in your everyday speech both in normal conversations and at work; I would recommend not downgrading from です and ます when speaking to someone like your boss or anyone in a higher position than you though.