ては

1. 1If X happens or is done, it leads to a bad, troublesome, or unacceptable outcome.Ex. 1
2. 2Used with evaluative expressions such as 困る to say that a situation would be a problem.Ex. 2
3. 3Describes a neutral repeated cycle of actions, as in 本を読んでは感想を書く ('read a book, then write a response, again and again').

Used in both speech and writing, and often contracted to ちゃ or じゃ in casual speech. In the conditional sense, the main clause typically expresses a negative evaluation such as 困る, 体に悪い, or だめだ, so it is common in warnings and advice. Unlike たら or と, this sense builds in an expectation of an unwelcome outcome. The repeated-action sense, as in 本を読んでは感想を書く, is neutral and simply describes a recurring cycle.

• ていてはN2「ていては」 covers only the conditional use of 「ては」, attaches only to verbs, and emphasizes that a continuing action or state will cause problems; 「ては」 can also attach to adjectives and nouns and has a repeated-alternation use, which 「ていては」 lacks.
• とN5「と」 is close to 「ては」 mainly in its conditional sense: 「と」 objectively states regularities, habits, or past discoveries, with outcomes that can be good or bad; 「ては」 focuses on anticipating an unfavorable result with a tone of worry or discouragement, so the two are generally not interchangeable.
• たらN4「たら」 is a neutral hypothetical conditional whose following clause can be good or bad and can express intention or requests; 「ては」 mostly signals an unfavorable outcome with a tone of worry or discouragement. 「たら」 can also mean 'after' or 'upon discovering', but has no repeated-alternation use.
• せいでN3「せいで」 blames a bad result on some cause with a tone of dissatisfaction, usually for things that have already happened; 「ては」 is a negative prediction about an action or situation, mostly expressing worry or discouragement, and also has a repeated meaning. The two cannot be swapped.
• てもN4「ても」 is a concessive contrast ('even if... still...') where the first clause does not affect the second; 「ては」 means that once the first clause occurs, an unfavorable result follows, and it also has a repeated use. Their conjugation patterns are parallel (くても／でも), but their meanings differ and they cannot be interchanged.

ていては stresses that continuing an ongoing or habitual action leads to a bad outcome, while と and たら are general conditionals that do not require a negative result. せいで blames a specific cause for a bad result, whereas conditional ては presents a condition and its unwelcome consequence, and ても is concessive ('even if') rather than a condition leading to trouble.