The "te" form is used when a speaker provides a condition or a reason of the action or the situation by using adjectives. It can be used both in negative sentences and in positive sentences. For example, 1. 足が痛くて、立てません。[Ashi ga itaku te tatemasen.] I can't stand up because my legs hurt. 2. 楽しくて、時間を忘れる。[Tanoshiku te Jikan wo wasureru.] I forgot about time because it was fun. In the first sentence, the 'te' form clause is providing a reason he or she cannot stand up, and the second one tells the reason the speaker forgot about time. You can create many sentences by adding 'te' to adjectives.

いたい[ adj ] おなかが　いたくて　たべられません。[ Onaka ga itakute taberaremasen. ] - I can't eat because I have a tummy ache. くらい[ adj ] くらくて　みえません。[ Kurakute miemasen. ] - I can't see because it is dark. たかい[ adj ] たかくて　かえません。[ Takakute kaemasen. ] - I can't buy it because it is expensive. いそがしい [ adj ] しごとが　いそがしくて　やすみが　とれません。[ Shigoto ga isogashikute yasumi ga toremasen. ] - I can't take days off work because I'm busy with work.