Kesalahan kecil bisa saja terjadi saat kita lelah, jadi jangan terlalu keras pada diri sendiri.

Both bisa and bisa saja can translate as "can / may", but bisa saja adds a nuance of “it’s quite possible / it just might happen”.

• Kesalahan kecil bisa terjadi
  = Small mistakes can happen. (neutral statement of possibility)

• Kesalahan kecil bisa saja terjadi
  = Small mistakes might very well happen / can easily happen.
  The saja softens it and makes it sound more like a natural, empathetic reassurance: “hey, it’s only natural that this could happen.”

Indonesian word order is quite flexible, but not completely free. In this structure:

• bisa = can
• saja = just / simply / even (here: softening, “might well”)
• terjadi = to happen

The natural order is:

bisa saja terjadi

Putting saja right after the modal (bisa) is common when saja modifies the degree or attitude toward the possibility, not the verb itself.

bisa terjadi saja sounds odd here and is not how a native speaker would say it. If you move saja, it usually changes the nuance or becomes ungrammatical.

All three can often be translated as “when we are tired”, but there are slight nuances:

• saat kita lelah

  • saat literally means “moment / time (point in time)”
  • quite neutral, common in both spoken and written Indonesian

• ketika kita lelah

  • ketika = when
  • slightly more formal/literary than saat, often used in writing or speeches, but also fine in speech

• waktu kita lelah

  • waktu = time
  • feels a bit more informal/colloquial here

In this sentence, you can naturally say:

• Kesalahan kecil bisa saja terjadi saat kita lelah…
• Kesalahan kecil bisa saja terjadi ketika kita lelah…
• Kesalahan kecil bisa saja terjadi waktu kita lelah…

All are correct; the choice is mostly about style and register.

Indonesian distinguishes between two kinds of we:

• kita = we (including the person you’re talking to)
• kami = we (excluding the person you’re talking to)

In saat kita lelah, the speaker is including the listener in the group:

• kita here suggests “when we (people in general, including you) are tired”.

If you used kami:

• saat kami lelah would mean “when we (but not you) are tired,”
  which doesn’t fit the comforting, inclusive tone of the sentence.

In Indonesian imperatives, the subject (you) is often left out because it’s understood from context.

• jangan terlalu keras pada diri sendiri
  literally: “don’t be too hard on yourself”
  The “you” is implied.

You could say:

• Jangan terlalu keras pada dirimu sendiri.
• Jangan terlalu keras pada kamu sendiri.

These explicitly mark “yourself” as second person, but the original sentence is more general and can apply to any listener (or even to oneself). Using diri sendiri without -mu keeps it slightly more neutral and universal, like a general life advice.

• diri = self
• sendiri = own / oneself

Together:

• diri sendiri = oneself / yourself / themselves, etc.

The preposition pada is needed because in Indonesian, certain adjectives or attitudes towards someone take pada:

• keras pada … = harsh / strict towards …

So:

• keras pada diri sendiri
  literally: harsh/strict towards oneself
  naturally translated: hard on yourself.

Without pada, keras diri sendiri would be ungrammatical or at least very unnatural in this meaning.

Yes. keras has several meanings, including:

1. Physically hard / solid

   • roti ini sudah keras = this bread has gone hard

2. Strong / intense (for sounds, actions, etc.)

   • suara musiknya keras = the music is loud
   • bekerja keras = to work hard

3. Harsh / strict / severe (about people or treatment)

   • orang tuanya sangat keras = their parents are very strict
   • jangan terlalu keras pada diri sendiri = don’t be too hard on yourself

So in this sentence, keras refers to being mentally/emotionally harsh toward yourself, not physical hardness.

jadi here functions as a conjunction meaning “so / therefore”:

• Kesalahan kecil bisa saja terjadi saat kita lelah, jadi jangan terlalu keras pada diri sendiri.
  = Small mistakes can happen when we are tired, so don’t be too hard on yourself.

Other similar connectors:

• maka (formal/literary)
• oleh karena itu (formal: “because of that / therefore”)

Using jadi gives the sentence a natural, conversational tone.

Yes. jangan is the standard way to form negative imperatives (telling someone not to do something).

Structure:

• jangan + verb / adjective phrase

Examples:

• Jangan pergi. = Don’t go.
• Jangan marah. = Don’t be angry.
• Jangan terlalu keras pada diri sendiri. = Don’t be too hard on yourself.

You don’t need to add a subject; the “you” is typically understood from context.

Indonesian usually does not mark plural if it’s clear from context.

• kesalahan kecil can mean “a small mistake” or “small mistakes”
  depending on context.

Reduplication (kesalahan-kesalahan) does exist to emphasize plurality, but:

• kesalahan kecil = small mistakes (general)
• kesalahan-kesalahan kecil = (various) small mistakes, with more emphasis on many or multiple distinct mistakes

In this sentence, the idea is general (“small mistakes can happen”), and there’s no need to stress exact number, so kesalahan kecil is the most natural choice.

Yes, but the nuance changes:

1. Removing saja:

   • Kesalahan kecil bisa saja terjadi…
     = Small mistakes might well happen / can easily happen.
   • Kesalahan kecil bisa terjadi…
     = Small mistakes can happen. (more neutral, slightly less soft/empathetic)

2. Removing terlalu:

   • Jangan terlalu keras pada diri sendiri.
     = Don’t be too hard on yourself.
   • Jangan keras pada diri sendiri.
     = Don’t be hard on yourself (at all).

The original version with saja and terlalu sounds more gentle and natural in a comforting context.

This sentence is neutral in register:

• Vocabulary is standard, not slang.
• Grammar is straightforward.
• No overly formal expressions.

You can use it in many situations:

• Talking to a friend or family member who made a mistake.
• In a supportive message: email, chat, social media.
• Even in semi-formal writing (blog posts, counseling material, motivational talk).

In very formal writing (official reports, academic writing), you might adjust style slightly, but this sentence would still generally be acceptable.