Worship (Ibadah) is the purpose behind our creation. As the Qur'an states, in Surah al-Dhariyat, verse 56: "I did not create the jinn and humans except that they may worship Me."
If the work we are doing is for the sake of seeking the pleasure of God, then it is an act of worship. It could be a business venture, the pursuit of knowledge, marriage, service to people...what makes it an act of worship (Ibadah) is the sacred motive behind it's performance. Worship is the nourishment of the soul and the best food for the body. Performing it with enthusiasm and presence of heart has profound benefits, to the heart, mind and soul.
The Holy Prophet is reported to have said: "Blessed is he who loves worship and is always fond of it."
Anyone can have communion with God at any time, under any circumstance, and without any prior arrangement and meditation. Although special times such as the time of dawn, sunset on Friday, after the deliverance of the Friday prayer sermons, when it is raining, and the Night of Qadr have particular importance for supplication(Dua) and worship(Ibadah); supplication adn devotion are not confined to these periods.
Worship, at any rate, is the medicine for negligence, oblivion and disobedience, and the source of tranquility for the heart, as mentioned in the Quran in Surah al-Ra'd, verse 28: "Look! The hearts find rest in Allah's remembrance!"
In conclusion, here are the words of Imam Ali (A) with regards to worship, from Nahjul Balaghah: "Certainly, prayer removes sins like autumn strips leaves off from trees, and it liberates you from the rope of sins tied around your neck."
"This act of worship gives the believing servants' limbs peace and rest, casts fear in their eyes, softens their spirits, cultivates a sense of humility in their hearts and purges them from pride. At the time of fear, anxiety and loneliness, remembrance of You (Allah) gives them enthusiasm and intimacy."