The longest book in the Bible, the book of Psalms, begins with the word blessed without giving any definition of what that term means (Psalm 1:1). In the second occurrence of the term, Psalm 2 ends with a statement about those who are blessed (Psalm 2:12) but it still does not tell us what the term means. The third occurrence of the term in the Psalms shows us what the core idea of the term is:
Psa 5:12 For thou, LORD, wilt bless the righteous;
with favour wilt thou compass him as with a shield.
The parallelism seen in these two statements about the righteous shows that to be blessed means to be in and enjoy a position of special favor with God.
Further analysis of Scriptural use of the term (e.g. Psalm 94:12; Matt. 5:4; Rev. 14:13) confirms this understanding and teaches us that being blessed does not mean having no troubles and having everything go the way you would like it to go. It does not necessarily mean being happy. Being a blessed person means to be someone whom God has favored in a special way!